From 38f002dd4676ff07e1565f60ebfc82761bb24589 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Tue, 15 Mar 2022 13:48:18 +0100
Subject: [PATCH 01/19] Removed existing resource inheritance tests

---
 .../ResourceInheritance/Book.cs               |  11 -
 .../CompanyHealthInsurance.cs                 |  11 -
 .../ResourceInheritance/ContentItem.cs        |  12 -
 .../FamilyHealthInsurance.cs                  |  11 -
 .../ResourceInheritance/HealthInsurance.cs    |  12 -
 .../ResourceInheritance/Human.cs              |  24 -
 .../InheritanceDbContext.cs                   |  38 --
 .../ResourceInheritance/InheritanceFakers.cs  |  55 ---
 .../ResourceInheritance/InheritanceTests.cs   | 458 ------------------
 .../ResourceInheritance/Man.cs                |  12 -
 .../ResourceInheritance/Video.cs              |  11 -
 .../ResourceInheritance/Woman.cs              |  11 -
 12 files changed, 666 deletions(-)
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Book.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/CompanyHealthInsurance.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ContentItem.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/FamilyHealthInsurance.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/HealthInsurance.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Human.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceDbContext.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceFakers.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceTests.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Man.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Video.cs
 delete mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Woman.cs

diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Book.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Book.cs
deleted file mode 100644
index f453b59915..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Book.cs
+++ /dev/null
@@ -1,11 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public sealed class Book : ContentItem
-{
-    [Attr]
-    public int PageCount { get; set; }
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/CompanyHealthInsurance.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/CompanyHealthInsurance.cs
deleted file mode 100644
index 53f6af49f7..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/CompanyHealthInsurance.cs
+++ /dev/null
@@ -1,11 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public sealed class CompanyHealthInsurance : HealthInsurance
-{
-    [Attr]
-    public string CompanyCode { get; set; } = null!;
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ContentItem.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ContentItem.cs
deleted file mode 100644
index 3dd1d00eaa..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ContentItem.cs
+++ /dev/null
@@ -1,12 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public abstract class ContentItem : Identifiable<int>
-{
-    [Attr]
-    public string Title { get; set; } = null!;
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/FamilyHealthInsurance.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/FamilyHealthInsurance.cs
deleted file mode 100644
index 4975835f69..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/FamilyHealthInsurance.cs
+++ /dev/null
@@ -1,11 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public sealed class FamilyHealthInsurance : HealthInsurance
-{
-    [Attr]
-    public int PermittedFamilySize { get; set; }
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/HealthInsurance.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/HealthInsurance.cs
deleted file mode 100644
index c194d5bb86..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/HealthInsurance.cs
+++ /dev/null
@@ -1,12 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public abstract class HealthInsurance : Identifiable<int>
-{
-    [Attr]
-    public bool HasMonthlyFee { get; set; }
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Human.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Human.cs
deleted file mode 100644
index d32d182dc4..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Human.cs
+++ /dev/null
@@ -1,24 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public abstract class Human : Identifiable<int>
-{
-    [Attr]
-    public string FamilyName { get; set; } = null!;
-
-    [Attr]
-    public bool IsRetired { get; set; }
-
-    [HasOne]
-    public HealthInsurance? HealthInsurance { get; set; }
-
-    [HasMany]
-    public ICollection<Human> Parents { get; set; } = new List<Human>();
-
-    [HasMany]
-    public ICollection<ContentItem> FavoriteContent { get; set; } = new List<ContentItem>();
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceDbContext.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceDbContext.cs
deleted file mode 100644
index ddf70ad29e..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceDbContext.cs
+++ /dev/null
@@ -1,38 +0,0 @@
-using JetBrains.Annotations;
-using Microsoft.EntityFrameworkCore;
-
-// @formatter:wrap_chained_method_calls chop_always
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public sealed class InheritanceDbContext : DbContext
-{
-    public DbSet<Human> Humans => Set<Human>();
-    public DbSet<Man> Men => Set<Man>();
-    public DbSet<CompanyHealthInsurance> CompanyHealthInsurances => Set<CompanyHealthInsurance>();
-    public DbSet<ContentItem> ContentItems => Set<ContentItem>();
-
-    public InheritanceDbContext(DbContextOptions<InheritanceDbContext> options)
-        : base(options)
-    {
-    }
-
-    protected override void OnModelCreating(ModelBuilder builder)
-    {
-        builder.Entity<Human>()
-            .HasDiscriminator<int>("Type")
-            .HasValue<Man>(1)
-            .HasValue<Woman>(2);
-
-        builder.Entity<HealthInsurance>()
-            .HasDiscriminator<int>("Type")
-            .HasValue<CompanyHealthInsurance>(1)
-            .HasValue<FamilyHealthInsurance>(2);
-
-        builder.Entity<ContentItem>()
-            .HasDiscriminator<int>("Type")
-            .HasValue<Video>(1)
-            .HasValue<Book>(2);
-    }
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceFakers.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceFakers.cs
deleted file mode 100644
index 8c88b8aa49..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceFakers.cs
+++ /dev/null
@@ -1,55 +0,0 @@
-using Bogus;
-using TestBuildingBlocks;
-
-// @formatter:wrap_chained_method_calls chop_always
-// @formatter:keep_existing_linebreaks true
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-internal sealed class InheritanceFakers : FakerContainer
-{
-    private readonly Lazy<Faker<Man>> _lazyManFaker = new(() =>
-        new Faker<Man>()
-            .UseSeed(GetFakerSeed())
-            .RuleFor(man => man.FamilyName, faker => faker.Person.LastName)
-            .RuleFor(man => man.IsRetired, faker => faker.Random.Bool())
-            .RuleFor(man => man.HasBeard, faker => faker.Random.Bool()));
-
-    private readonly Lazy<Faker<Woman>> _lazyWomanFaker = new(() =>
-        new Faker<Woman>()
-            .UseSeed(GetFakerSeed())
-            .RuleFor(woman => woman.FamilyName, faker => faker.Person.LastName)
-            .RuleFor(woman => woman.IsRetired, faker => faker.Random.Bool())
-            .RuleFor(woman => woman.IsPregnant, faker => faker.Random.Bool()));
-
-    private readonly Lazy<Faker<Book>> _lazyBookFaker = new(() =>
-        new Faker<Book>()
-            .UseSeed(GetFakerSeed())
-            .RuleFor(book => book.Title, faker => faker.Commerce.ProductName())
-            .RuleFor(book => book.PageCount, faker => faker.Random.Int(50, 150)));
-
-    private readonly Lazy<Faker<Video>> _lazyVideoFaker = new(() =>
-        new Faker<Video>()
-            .UseSeed(GetFakerSeed())
-            .RuleFor(video => video.Title, faker => faker.Commerce.ProductName())
-            .RuleFor(video => video.DurationInSeconds, faker => faker.Random.Int(250, 750)));
-
-    private readonly Lazy<Faker<FamilyHealthInsurance>> _lazyFamilyHealthInsuranceFaker = new(() =>
-        new Faker<FamilyHealthInsurance>()
-            .UseSeed(GetFakerSeed())
-            .RuleFor(familyHealthInsurance => familyHealthInsurance.HasMonthlyFee, faker => faker.Random.Bool())
-            .RuleFor(familyHealthInsurance => familyHealthInsurance.PermittedFamilySize, faker => faker.Random.Int(2, 10)));
-
-    private readonly Lazy<Faker<CompanyHealthInsurance>> _lazyCompanyHealthInsuranceFaker = new(() =>
-        new Faker<CompanyHealthInsurance>()
-            .UseSeed(GetFakerSeed())
-            .RuleFor(companyHealthInsurance => companyHealthInsurance.HasMonthlyFee, faker => faker.Random.Bool())
-            .RuleFor(companyHealthInsurance => companyHealthInsurance.CompanyCode, faker => faker.Company.CompanyName()));
-
-    public Faker<Man> Man => _lazyManFaker.Value;
-    public Faker<Woman> Woman => _lazyWomanFaker.Value;
-    public Faker<Book> Book => _lazyBookFaker.Value;
-    public Faker<Video> Video => _lazyVideoFaker.Value;
-    public Faker<FamilyHealthInsurance> FamilyHealthInsurance => _lazyFamilyHealthInsuranceFaker.Value;
-    public Faker<CompanyHealthInsurance> CompanyHealthInsurance => _lazyCompanyHealthInsuranceFaker.Value;
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceTests.cs
deleted file mode 100644
index 0aed279351..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/InheritanceTests.cs
+++ /dev/null
@@ -1,458 +0,0 @@
-using System.Net;
-using FluentAssertions;
-using JsonApiDotNetCore.Serialization.Objects;
-using Microsoft.EntityFrameworkCore;
-using TestBuildingBlocks;
-using Xunit;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-public sealed class InheritanceTests : IClassFixture<IntegrationTestContext<TestableStartup<InheritanceDbContext>, InheritanceDbContext>>
-{
-    private readonly IntegrationTestContext<TestableStartup<InheritanceDbContext>, InheritanceDbContext> _testContext;
-    private readonly InheritanceFakers _fakers = new();
-
-    public InheritanceTests(IntegrationTestContext<TestableStartup<InheritanceDbContext>, InheritanceDbContext> testContext)
-    {
-        _testContext = testContext;
-
-        testContext.UseController<MenController>();
-    }
-
-    [Fact]
-    public async Task Can_create_resource_with_inherited_attributes()
-    {
-        // Arrange
-        Man newMan = _fakers.Man.Generate();
-
-        var requestBody = new
-        {
-            data = new
-            {
-                type = "men",
-                attributes = new
-                {
-                    familyName = newMan.FamilyName,
-                    isRetired = newMan.IsRetired,
-                    hasBeard = newMan.HasBeard
-                }
-            }
-        };
-
-        const string route = "/men";
-
-        // Act
-        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
-
-        responseDocument.Data.SingleValue.ShouldNotBeNull();
-        responseDocument.Data.SingleValue.Type.Should().Be("men");
-        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("familyName").With(value => value.Should().Be(newMan.FamilyName));
-        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("isRetired").With(value => value.Should().Be(newMan.IsRetired));
-        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("hasBeard").With(value => value.Should().Be(newMan.HasBeard));
-
-        int newManId = int.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.FirstWithIdAsync(newManId);
-
-            manInDatabase.FamilyName.Should().Be(newMan.FamilyName);
-            manInDatabase.IsRetired.Should().Be(newMan.IsRetired);
-            manInDatabase.HasBeard.Should().Be(newMan.HasBeard);
-        });
-    }
-
-    [Fact]
-    public async Task Can_create_resource_with_ToOne_relationship()
-    {
-        // Arrange
-        CompanyHealthInsurance existingInsurance = _fakers.CompanyHealthInsurance.Generate();
-
-        string newFamilyName = _fakers.Man.Generate().FamilyName;
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            await dbContext.ClearTableAsync<CompanyHealthInsurance>();
-            dbContext.CompanyHealthInsurances.Add(existingInsurance);
-            await dbContext.SaveChangesAsync();
-        });
-
-        var requestBody = new
-        {
-            data = new
-            {
-                type = "men",
-                attributes = new
-                {
-                    familyName = newFamilyName
-                },
-                relationships = new
-                {
-                    healthInsurance = new
-                    {
-                        data = new
-                        {
-                            type = "companyHealthInsurances",
-                            id = existingInsurance.StringId
-                        }
-                    }
-                }
-            }
-        };
-
-        const string route = "/men";
-
-        // Act
-        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
-
-        responseDocument.Data.SingleValue.ShouldNotBeNull();
-        int newManId = int.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.Include(man => man.HealthInsurance).FirstWithIdAsync(newManId);
-
-            manInDatabase.HealthInsurance.ShouldNotBeNull();
-            manInDatabase.HealthInsurance.Should().BeOfType<CompanyHealthInsurance>();
-            manInDatabase.HealthInsurance.Id.Should().Be(existingInsurance.Id);
-        });
-    }
-
-    [Fact]
-    public async Task Can_update_resource()
-    {
-        // Arrange
-        Man existingMan = _fakers.Man.Generate();
-
-        Man newMan = _fakers.Man.Generate();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            dbContext.Men.Add(existingMan);
-            await dbContext.SaveChangesAsync();
-        });
-
-        var requestBody = new
-        {
-            data = new
-            {
-                type = "men",
-                id = existingMan.StringId,
-                attributes = new
-                {
-                    familyName = newMan.FamilyName,
-                    isRetired = newMan.IsRetired,
-                    hasBeard = newMan.HasBeard
-                }
-            }
-        };
-
-        string route = $"/men/{existingMan.StringId}";
-
-        // Act
-        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
-
-        responseDocument.Should().BeEmpty();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.FirstWithIdAsync(existingMan.Id);
-
-            manInDatabase.FamilyName.Should().Be(newMan.FamilyName);
-            manInDatabase.IsRetired.Should().Be(newMan.IsRetired);
-            manInDatabase.HasBeard.Should().Be(newMan.HasBeard);
-        });
-    }
-
-    [Fact]
-    public async Task Can_assign_ToOne_relationship()
-    {
-        // Arrange
-        Man existingMan = _fakers.Man.Generate();
-        FamilyHealthInsurance existingInsurance = _fakers.FamilyHealthInsurance.Generate();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            await dbContext.ClearTablesAsync<Man, CompanyHealthInsurance>();
-            dbContext.AddInRange(existingMan, existingInsurance);
-            await dbContext.SaveChangesAsync();
-        });
-
-        var requestBody = new
-        {
-            data = new
-            {
-                type = "familyHealthInsurances",
-                id = existingInsurance.StringId
-            }
-        };
-
-        string route = $"/men/{existingMan.StringId}/relationships/healthInsurance";
-
-        // Act
-        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
-
-        responseDocument.Should().BeEmpty();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.Include(man => man.HealthInsurance).FirstWithIdAsync(existingMan.Id);
-
-            manInDatabase.HealthInsurance.ShouldNotBeNull();
-            manInDatabase.HealthInsurance.Should().BeOfType<FamilyHealthInsurance>();
-            manInDatabase.HealthInsurance.Id.Should().Be(existingInsurance.Id);
-        });
-    }
-
-    [Fact]
-    public async Task Can_create_resource_with_OneToMany_relationship()
-    {
-        // Arrange
-        Man existingFather = _fakers.Man.Generate();
-        Woman existingMother = _fakers.Woman.Generate();
-
-        string newFamilyName = _fakers.Man.Generate().FamilyName;
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            await dbContext.ClearTablesAsync<Woman, Man>();
-            dbContext.Humans.AddRange(existingFather, existingMother);
-            await dbContext.SaveChangesAsync();
-        });
-
-        var requestBody = new
-        {
-            data = new
-            {
-                type = "men",
-                attributes = new
-                {
-                    familyName = newFamilyName
-                },
-                relationships = new
-                {
-                    parents = new
-                    {
-                        data = new[]
-                        {
-                            new
-                            {
-                                type = "men",
-                                id = existingFather.StringId
-                            },
-                            new
-                            {
-                                type = "women",
-                                id = existingMother.StringId
-                            }
-                        }
-                    }
-                }
-            }
-        };
-
-        const string route = "/men";
-
-        // Act
-        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
-
-        responseDocument.Data.SingleValue.ShouldNotBeNull();
-        int newManId = int.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.Include(man => man.Parents).FirstWithIdAsync(newManId);
-
-            manInDatabase.Parents.ShouldHaveCount(2);
-            manInDatabase.Parents.Should().ContainSingle(human => human is Man);
-            manInDatabase.Parents.Should().ContainSingle(human => human is Woman);
-        });
-    }
-
-    [Fact]
-    public async Task Can_assign_OneToMany_relationship()
-    {
-        // Arrange
-        Man existingChild = _fakers.Man.Generate();
-        Man existingFather = _fakers.Man.Generate();
-        Woman existingMother = _fakers.Woman.Generate();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            await dbContext.ClearTablesAsync<Woman, Man>();
-            dbContext.Humans.AddRange(existingChild, existingFather, existingMother);
-            await dbContext.SaveChangesAsync();
-        });
-
-        var requestBody = new
-        {
-            data = new[]
-            {
-                new
-                {
-                    type = "men",
-                    id = existingFather.StringId
-                },
-                new
-                {
-                    type = "women",
-                    id = existingMother.StringId
-                }
-            }
-        };
-
-        string route = $"/men/{existingChild.StringId}/relationships/parents";
-
-        // Act
-        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
-
-        responseDocument.Should().BeEmpty();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.Include(man => man.Parents).FirstWithIdAsync(existingChild.Id);
-
-            manInDatabase.Parents.ShouldHaveCount(2);
-            manInDatabase.Parents.Should().ContainSingle(human => human is Man);
-            manInDatabase.Parents.Should().ContainSingle(human => human is Woman);
-        });
-    }
-
-    [Fact]
-    public async Task Can_create_resource_with_ManyToMany_relationship()
-    {
-        // Arrange
-        Book existingBook = _fakers.Book.Generate();
-        Video existingVideo = _fakers.Video.Generate();
-
-        string newFamilyName = _fakers.Man.Generate().FamilyName;
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            await dbContext.ClearTablesAsync<Book, Video, Man>();
-            dbContext.ContentItems.AddRange(existingBook, existingVideo);
-            await dbContext.SaveChangesAsync();
-        });
-
-        var requestBody = new
-        {
-            data = new
-            {
-                type = "men",
-                attributes = new
-                {
-                    familyName = newFamilyName
-                },
-                relationships = new
-                {
-                    favoriteContent = new
-                    {
-                        data = new[]
-                        {
-                            new
-                            {
-                                type = "books",
-                                id = existingBook.StringId
-                            },
-                            new
-                            {
-                                type = "videos",
-                                id = existingVideo.StringId
-                            }
-                        }
-                    }
-                }
-            }
-        };
-
-        const string route = "/men";
-
-        // Act
-        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
-
-        responseDocument.Data.SingleValue.ShouldNotBeNull();
-        int newManId = int.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.Include(man => man.FavoriteContent).FirstWithIdAsync(newManId);
-
-            manInDatabase.FavoriteContent.ShouldHaveCount(2);
-            manInDatabase.FavoriteContent.Should().ContainSingle(item => item is Book && item.Id == existingBook.Id);
-            manInDatabase.FavoriteContent.Should().ContainSingle(item => item is Video && item.Id == existingVideo.Id);
-        });
-    }
-
-    [Fact]
-    public async Task Can_assign_ManyToMany_relationship()
-    {
-        // Arrange
-        Book existingBook = _fakers.Book.Generate();
-        Video existingVideo = _fakers.Video.Generate();
-        Man existingMan = _fakers.Man.Generate();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            await dbContext.ClearTablesAsync<Book, Video, Man>();
-            dbContext.AddInRange(existingBook, existingVideo, existingMan);
-            await dbContext.SaveChangesAsync();
-        });
-
-        var requestBody = new
-        {
-            data = new[]
-            {
-                new
-                {
-                    type = "books",
-                    id = existingBook.StringId
-                },
-                new
-                {
-                    type = "videos",
-                    id = existingVideo.StringId
-                }
-            }
-        };
-
-        string route = $"/men/{existingMan.StringId}/relationships/favoriteContent";
-
-        // Act
-        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
-
-        // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
-
-        responseDocument.Should().BeEmpty();
-
-        await _testContext.RunOnDatabaseAsync(async dbContext =>
-        {
-            Man manInDatabase = await dbContext.Men.Include(man => man.FavoriteContent).FirstWithIdAsync(existingMan.Id);
-
-            manInDatabase.FavoriteContent.ShouldHaveCount(2);
-            manInDatabase.FavoriteContent.Should().ContainSingle(item => item is Book && item.Id == existingBook.Id);
-            manInDatabase.FavoriteContent.Should().ContainSingle(item => item is Video && item.Id == existingVideo.Id);
-        });
-    }
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Man.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Man.cs
deleted file mode 100644
index 7a2ca673eb..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Man.cs
+++ /dev/null
@@ -1,12 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
-public sealed class Man : Human
-{
-    [Attr]
-    public bool HasBeard { get; set; }
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Video.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Video.cs
deleted file mode 100644
index 606bc942f6..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Video.cs
+++ /dev/null
@@ -1,11 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public sealed class Video : ContentItem
-{
-    [Attr]
-    public int DurationInSeconds { get; set; }
-}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Woman.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Woman.cs
deleted file mode 100644
index 9c33a16cd9..0000000000
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Woman.cs
+++ /dev/null
@@ -1,11 +0,0 @@
-using JetBrains.Annotations;
-using JsonApiDotNetCore.Resources.Annotations;
-
-namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
-
-[UsedImplicitly(ImplicitUseTargetFlags.Members)]
-public sealed class Woman : Human
-{
-    [Attr]
-    public bool IsPregnant { get; set; }
-}

From f9acef95c2460c108ddd566086dcbf898e0edea4 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Tue, 15 Mar 2022 15:40:31 +0100
Subject: [PATCH 02/19] Resource inheritance: return derived types

---
 .../Configuration/ResourceType.cs             |  53 +-
 .../Configuration/ResourceGraphBuilder.cs     |  37 +-
 .../Response/ResponseModelAdapter.cs          |  27 +-
 .../Models/BicycleLight.cs                    |  13 +
 .../ResourceInheritance/Models/Bike.cs        |  21 +
 .../ResourceInheritance/Models/Box.cs         |  19 +
 .../ResourceInheritance/Models/Car.cs         |  15 +
 .../ResourceInheritance/Models/CarbonWheel.cs |  12 +
 .../ResourceInheritance/Models/ChromeWheel.cs |  12 +
 .../ResourceInheritance/Models/Cylinder.cs    |  13 +
 .../Models/DieselEngine.cs                    |  18 +
 .../ResourceInheritance/Models/Engine.cs      |  16 +
 .../Models/GasolineEngine.cs                  |  21 +
 .../Models/GenericFeature.cs                  |  16 +
 .../Models/GenericProperty.cs                 |  13 +
 .../Models/MotorVehicle.cs                    |  21 +
 .../Models/NavigationSystem.cs                |  13 +
 .../Models/NumberProperty.cs                  |  12 +
 .../ResourceInheritance/Models/NumberValue.cs |  13 +
 .../Models/StringProperty.cs                  |  12 +
 .../ResourceInheritance/Models/StringValue.cs |  13 +
 .../ResourceInheritance/Models/Tandem.cs      |  15 +
 .../ResourceInheritance/Models/Truck.cs       |  18 +
 .../ResourceInheritance/Models/Vehicle.cs     |  22 +
 .../Models/VehicleManufacturer.cs             |  16 +
 .../ResourceInheritance/Models/Wheel.cs       |  16 +
 .../ResourceInheritanceDbContext.cs           |  33 +
 .../ResourceInheritanceFakers.cs              | 141 +++++
 .../ResourceInheritanceTests.cs               | 583 ++++++++++++++++++
 .../TablePerHierarchyDbContext.cs             |  13 +
 .../TablePerHierarchyTests.cs                 |  13 +
 .../TablePerType/TablePerTypeDbContext.cs     |  36 ++
 .../TablePerType/TablePerTypeTests.cs         |  13 +
 .../Serialization/Response/FakeLinkBuilder.cs |  25 +
 .../Serialization/Response/FakeMetaBuilder.cs |  15 +
 .../FakeRequestQueryStringAccessor.cs         |   9 +
 .../FakeResourceDefinitionAccessor.cs         | 100 +++
 .../Response/IncompleteResourceGraphTests.cs  |  64 ++
 .../Response/ResponseModelAdapterTests.cs     | 132 ----
 .../TestBuildingBlocks/DbContextExtensions.cs |   8 -
 .../NullabilityAssertionExtensions.cs         |   7 +
 41 files changed, 1521 insertions(+), 148 deletions(-)
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/BicycleLight.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Bike.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Box.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Car.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/CarbonWheel.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/ChromeWheel.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Cylinder.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/DieselEngine.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Engine.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GasolineEngine.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericFeature.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericProperty.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/MotorVehicle.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NavigationSystem.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberProperty.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberValue.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringProperty.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringValue.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Tandem.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Truck.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Vehicle.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Wheel.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyDbContext.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyTests.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeDbContext.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeTests.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeLinkBuilder.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeMetaBuilder.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeRequestQueryStringAccessor.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/IncompleteResourceGraphTests.cs

diff --git a/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs b/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
index ce7ccd1870..6c40c16b0f 100644
--- a/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
+++ b/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
@@ -11,6 +11,7 @@ public sealed class ResourceType
 {
     private readonly Dictionary<string, ResourceFieldAttribute> _fieldsByPublicName = new();
     private readonly Dictionary<string, ResourceFieldAttribute> _fieldsByPropertyName = new();
+    private readonly Lazy<IReadOnlySet<ResourceType>> _lazyAllConcreteDerivedTypes;
 
     /// <summary>
     /// The publicly exposed resource name.
@@ -28,22 +29,35 @@ public sealed class ResourceType
     public Type IdentityClrType { get; }
 
     /// <summary>
-    /// Exposed resource attributes and relationships. See https://jsonapi.org/format/#document-resource-object-fields.
+    /// The base resource type, in case this is a derived type.
+    /// </summary>
+    public ResourceType? BaseType { get; internal set; }
+
+    /// <summary>
+    /// The resource types that directly derive from this one.
+    /// </summary>
+    public IReadOnlySet<ResourceType> DirectlyDerivedTypes { get; internal set; } = new HashSet<ResourceType>();
+
+    /// <summary>
+    /// Exposed resource attributes and relationships. See https://jsonapi.org/format/#document-resource-object-fields. When using resource inheritance, this
+    /// includes the attributes and relationships from base types.
     /// </summary>
     public IReadOnlyCollection<ResourceFieldAttribute> Fields { get; }
 
     /// <summary>
-    /// Exposed resource attributes. See https://jsonapi.org/format/#document-resource-object-attributes.
+    /// Exposed resource attributes. See https://jsonapi.org/format/#document-resource-object-attributes. When using resource inheritance, this includes the
+    /// attributes from base types.
     /// </summary>
     public IReadOnlyCollection<AttrAttribute> Attributes { get; }
 
     /// <summary>
-    /// Exposed resource relationships. See https://jsonapi.org/format/#document-resource-object-relationships.
+    /// Exposed resource relationships. See https://jsonapi.org/format/#document-resource-object-relationships. When using resource inheritance, this
+    /// includes the relationships from base types.
     /// </summary>
     public IReadOnlyCollection<RelationshipAttribute> Relationships { get; }
 
     /// <summary>
-    /// Related entities that are not exposed as resource relationships.
+    /// Related entities that are not exposed as resource relationships. When using resource inheritance, this includes the eager-loads from base types.
     /// </summary>
     public IReadOnlyCollection<EagerLoadAttribute> EagerLoads { get; }
 
@@ -100,6 +114,29 @@ public ResourceType(string publicName, Type clrType, Type identityClrType, IRead
             _fieldsByPublicName.Add(field.PublicName, field);
             _fieldsByPropertyName.Add(field.Property.Name, field);
         }
+
+        _lazyAllConcreteDerivedTypes = new Lazy<IReadOnlySet<ResourceType>>(ResolveAllConcreteDerivedTypes, LazyThreadSafetyMode.PublicationOnly);
+    }
+
+    private IReadOnlySet<ResourceType> ResolveAllConcreteDerivedTypes()
+    {
+        var allConcreteDerivedTypes = new HashSet<ResourceType>();
+        AddConcreteDerivedTypes(this, allConcreteDerivedTypes);
+
+        return allConcreteDerivedTypes;
+    }
+
+    private static void AddConcreteDerivedTypes(ResourceType resourceType, ISet<ResourceType> allConcreteDerivedTypes)
+    {
+        foreach (ResourceType derivedType in resourceType.DirectlyDerivedTypes)
+        {
+            if (!derivedType.ClrType.IsAbstract)
+            {
+                allConcreteDerivedTypes.Add(derivedType);
+            }
+
+            AddConcreteDerivedTypes(derivedType, allConcreteDerivedTypes);
+        }
     }
 
     public AttrAttribute GetAttributeByPublicName(string publicName)
@@ -161,6 +198,14 @@ public RelationshipAttribute GetRelationshipByPropertyName(string propertyName)
             : null;
     }
 
+    /// <summary>
+    /// Returns all directly and indirectly non-abstract resource types that derive from this resource type.
+    /// </summary>
+    public IReadOnlySet<ResourceType> GetAllConcreteDerivedTypes()
+    {
+        return _lazyAllConcreteDerivedTypes.Value;
+    }
+
     public override string ToString()
     {
         return PublicName;
diff --git a/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs b/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
index 1352160f11..f4ac78049d 100644
--- a/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
+++ b/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
@@ -43,7 +43,15 @@ public IResourceGraph Build()
 
         var resourceGraph = new ResourceGraph(resourceTypes);
 
-        foreach (RelationshipAttribute relationship in resourceTypes.SelectMany(resourceType => resourceType.Relationships))
+        SetRelationshipTypes(resourceGraph);
+        SetDirectlyDerivedTypes(resourceGraph);
+
+        return resourceGraph;
+    }
+
+    private static void SetRelationshipTypes(ResourceGraph resourceGraph)
+    {
+        foreach (RelationshipAttribute relationship in resourceGraph.GetResourceTypes().SelectMany(resourceType => resourceType.Relationships))
         {
             relationship.LeftType = resourceGraph.GetResourceType(relationship.LeftClrType!);
             ResourceType? rightType = resourceGraph.FindResourceType(relationship.RightClrType!);
@@ -56,8 +64,33 @@ public IResourceGraph Build()
 
             relationship.RightType = rightType;
         }
+    }
 
-        return resourceGraph;
+    private static void SetDirectlyDerivedTypes(ResourceGraph resourceGraph)
+    {
+        Dictionary<ResourceType, HashSet<ResourceType>> directlyDerivedTypesPerBaseType = new();
+
+        foreach (ResourceType resourceType in resourceGraph.GetResourceTypes())
+        {
+            ResourceType? baseType = resourceGraph.FindResourceType(resourceType.ClrType.BaseType!);
+
+            if (baseType != null)
+            {
+                resourceType.BaseType = baseType;
+
+                if (!directlyDerivedTypesPerBaseType.ContainsKey(baseType))
+                {
+                    directlyDerivedTypesPerBaseType[baseType] = new HashSet<ResourceType>();
+                }
+
+                directlyDerivedTypesPerBaseType[baseType].Add(resourceType);
+            }
+        }
+
+        foreach ((ResourceType baseType, HashSet<ResourceType> directlyDerivedTypes) in directlyDerivedTypesPerBaseType)
+        {
+            baseType.DirectlyDerivedTypes = directlyDerivedTypes;
+        }
     }
 
     public ResourceGraphBuilder Add(DbContext dbContext)
diff --git a/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs b/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
index d881668c9f..0e1968821f 100644
--- a/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
+++ b/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
@@ -3,6 +3,7 @@
 using JetBrains.Annotations;
 using JsonApiDotNetCore.AtomicOperations;
 using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
 using JsonApiDotNetCore.Middleware;
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Queries.Internal;
@@ -172,8 +173,11 @@ private ResourceObjectTreeNode GetOrCreateTreeNode(IIdentifiable resource, Resou
     {
         if (!_resourceToTreeNodeCache.TryGetValue(resource, out ResourceObjectTreeNode? treeNode))
         {
-            ResourceObject resourceObject = ConvertResource(resource, resourceType, kind);
-            treeNode = new ResourceObjectTreeNode(resource, resourceType, resourceObject);
+            // In case of resource inheritance, prefer the derived resource type over the base type.
+            ResourceType effectiveResourceType = GetEffectiveResourceType(resource, resourceType);
+
+            ResourceObject resourceObject = ConvertResource(resource, effectiveResourceType, kind);
+            treeNode = new ResourceObjectTreeNode(resource, effectiveResourceType, resourceObject);
 
             _resourceToTreeNodeCache.Add(resource, treeNode);
         }
@@ -181,6 +185,25 @@ private ResourceObjectTreeNode GetOrCreateTreeNode(IIdentifiable resource, Resou
         return treeNode;
     }
 
+    private static ResourceType GetEffectiveResourceType(IIdentifiable resource, ResourceType declaredType)
+    {
+        Type runtimeResourceType = resource.GetType();
+
+        if (declaredType.ClrType == runtimeResourceType)
+        {
+            return declaredType;
+        }
+
+        ResourceType? derivedType = declaredType.GetAllConcreteDerivedTypes().FirstOrDefault(type => type.ClrType == runtimeResourceType);
+
+        if (derivedType == null)
+        {
+            throw new InvalidConfigurationException($"Type '{runtimeResourceType}' does not exist in the resource graph.");
+        }
+
+        return derivedType;
+    }
+
     protected virtual ResourceObject ConvertResource(IIdentifiable resource, ResourceType resourceType, EndpointKind kind)
     {
         bool isRelationship = kind == EndpointKind.Relationship;
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/BicycleLight.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/BicycleLight.cs
new file mode 100644
index 0000000000..f1d41f44af
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/BicycleLight.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class BicycleLight : Identifiable<long>
+{
+    [Attr]
+    public string Color { get; set; } = null!;
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Bike.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Bike.cs
new file mode 100644
index 0000000000..7416530409
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Bike.cs
@@ -0,0 +1,21 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public class Bike : Vehicle
+{
+    [Attr]
+    public override bool RequiresDriverLicense { get; set; }
+
+    [Attr]
+    public int GearCount { get; set; }
+
+    [HasOne]
+    public Box? CargoBox { get; set; }
+
+    [HasMany]
+    public ISet<BicycleLight> Lights { get; set; } = new HashSet<BicycleLight>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Box.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Box.cs
new file mode 100644
index 0000000000..872808badd
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Box.cs
@@ -0,0 +1,19 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class Box : Identifiable<long>
+{
+    [Attr]
+    public decimal Width { get; set; }
+
+    [Attr]
+    public decimal Height { get; set; }
+
+    [Attr]
+    public decimal Depth { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Car.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Car.cs
new file mode 100644
index 0000000000..4c10ff6868
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Car.cs
@@ -0,0 +1,15 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class Car : MotorVehicle
+{
+    [Attr]
+    public int SeatCount { get; set; }
+
+    [HasMany]
+    public ISet<GenericFeature> Features { get; set; } = new HashSet<GenericFeature>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/CarbonWheel.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/CarbonWheel.cs
new file mode 100644
index 0000000000..1f45e6875c
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/CarbonWheel.cs
@@ -0,0 +1,12 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class CarbonWheel : Wheel
+{
+    [Attr]
+    public bool HasTube { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/ChromeWheel.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/ChromeWheel.cs
new file mode 100644
index 0000000000..52b777bd87
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/ChromeWheel.cs
@@ -0,0 +1,12 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class ChromeWheel : Wheel
+{
+    [Attr]
+    public string? PaintColor { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Cylinder.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Cylinder.cs
new file mode 100644
index 0000000000..39019ac1f7
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Cylinder.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class Cylinder : Identifiable<long>
+{
+    [Attr]
+    public int SparkPlugCount { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/DieselEngine.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/DieselEngine.cs
new file mode 100644
index 0000000000..9cbb28c7a1
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/DieselEngine.cs
@@ -0,0 +1,18 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class DieselEngine : Engine
+{
+    [Attr]
+    public override bool IsHydrocarbonBased { get; set; }
+
+    [Attr]
+    public string? SerialCode { get; set; }
+
+    [Attr]
+    public decimal Viscosity { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Engine.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Engine.cs
new file mode 100644
index 0000000000..341c972ed5
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Engine.cs
@@ -0,0 +1,16 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public abstract class Engine : Identifiable<long>
+{
+    [Attr]
+    public abstract bool IsHydrocarbonBased { get; set; }
+
+    [Attr]
+    public decimal Capacity { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GasolineEngine.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GasolineEngine.cs
new file mode 100644
index 0000000000..ab296179cf
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GasolineEngine.cs
@@ -0,0 +1,21 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class GasolineEngine : Engine
+{
+    [Attr]
+    public override bool IsHydrocarbonBased { get; set; }
+
+    [Attr]
+    public string? SerialCode { get; set; }
+
+    [Attr]
+    public decimal Volatility { get; set; }
+
+    [HasMany]
+    public ISet<Cylinder> Cylinders { get; set; } = new HashSet<Cylinder>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericFeature.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericFeature.cs
new file mode 100644
index 0000000000..79de2d858e
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericFeature.cs
@@ -0,0 +1,16 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class GenericFeature : Identifiable<long>
+{
+    [Attr]
+    public string Description { get; set; } = null!;
+
+    [HasMany]
+    public ISet<GenericProperty> Properties { get; set; } = new HashSet<GenericProperty>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericProperty.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericProperty.cs
new file mode 100644
index 0000000000..e410b9a803
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/GenericProperty.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public abstract class GenericProperty : Identifiable<long>
+{
+    [Attr]
+    public string Name { get; set; } = null!;
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/MotorVehicle.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/MotorVehicle.cs
new file mode 100644
index 0000000000..2578d5d128
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/MotorVehicle.cs
@@ -0,0 +1,21 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public abstract class MotorVehicle : Vehicle
+{
+    [Attr]
+    public override bool RequiresDriverLicense { get; set; }
+
+    [Attr]
+    public string LicensePlate { get; set; } = null!;
+
+    [HasOne]
+    public Engine Engine { get; set; } = null!;
+
+    [HasOne]
+    public NavigationSystem? NavigationSystem { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NavigationSystem.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NavigationSystem.cs
new file mode 100644
index 0000000000..015c1089c7
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NavigationSystem.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class NavigationSystem : Identifiable<long>
+{
+    [Attr]
+    public string ModelType { get; set; } = null!;
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberProperty.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberProperty.cs
new file mode 100644
index 0000000000..e3d924f206
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberProperty.cs
@@ -0,0 +1,12 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class NumberProperty : GenericProperty
+{
+    [HasOne]
+    public NumberValue Value { get; set; } = null!;
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberValue.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberValue.cs
new file mode 100644
index 0000000000..c658d39137
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/NumberValue.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class NumberValue : Identifiable<long>
+{
+    [Attr]
+    public decimal Content { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringProperty.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringProperty.cs
new file mode 100644
index 0000000000..a145d17978
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringProperty.cs
@@ -0,0 +1,12 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class StringProperty : GenericProperty
+{
+    [HasOne]
+    public StringValue Value { get; set; } = null!;
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringValue.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringValue.cs
new file mode 100644
index 0000000000..fc620f7bd2
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/StringValue.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class StringValue : Identifiable<long>
+{
+    [Attr]
+    public string Content { get; set; } = null!;
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Tandem.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Tandem.cs
new file mode 100644
index 0000000000..e5c3247244
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Tandem.cs
@@ -0,0 +1,15 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class Tandem : Bike
+{
+    [Attr]
+    public int PassengerCount { get; set; }
+
+    [HasMany]
+    public ISet<GenericFeature> Features { get; set; } = new HashSet<GenericFeature>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Truck.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Truck.cs
new file mode 100644
index 0000000000..7a4df5f3e2
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Truck.cs
@@ -0,0 +1,18 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class Truck : MotorVehicle
+{
+    [Attr]
+    public decimal LoadingCapacity { get; set; }
+
+    [HasOne]
+    public Box? SleepingArea { get; set; }
+
+    [HasMany]
+    public ISet<GenericFeature> Features { get; set; } = new HashSet<GenericFeature>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Vehicle.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Vehicle.cs
new file mode 100644
index 0000000000..607dd68384
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Vehicle.cs
@@ -0,0 +1,22 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public abstract class Vehicle : Identifiable<long>
+{
+    [Attr]
+    public decimal Weight { get; set; }
+
+    [Attr]
+    public abstract bool RequiresDriverLicense { get; set; }
+
+    [HasOne]
+    public VehicleManufacturer? Manufacturer { get; set; }
+
+    [HasMany]
+    public ISet<Wheel> Wheels { get; set; } = new HashSet<Wheel>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs
new file mode 100644
index 0000000000..f18654b68c
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs
@@ -0,0 +1,16 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class VehicleManufacturer : Identifiable<long>
+{
+    [Attr]
+    public string Name { get; set; } = null!;
+
+    [HasMany]
+    public ISet<Vehicle> Vehicles { get; set; } = new HashSet<Vehicle>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Wheel.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Wheel.cs
new file mode 100644
index 0000000000..27e564a156
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/Wheel.cs
@@ -0,0 +1,16 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public abstract class Wheel : Identifiable<long>
+{
+    [Attr]
+    public decimal Radius { get; set; }
+
+    [HasOne]
+    public Vehicle? Vehicle { get; set; }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs
new file mode 100644
index 0000000000..958304e6c7
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs
@@ -0,0 +1,33 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+public abstract class ResourceInheritanceDbContext : DbContext
+{
+    public DbSet<Vehicle> Vehicles => Set<Vehicle>();
+    public DbSet<Bike> Bikes => Set<Bike>();
+    public DbSet<Tandem> Tandems => Set<Tandem>();
+    public DbSet<MotorVehicle> MotorVehicles => Set<MotorVehicle>();
+    public DbSet<Car> Cars => Set<Car>();
+    public DbSet<Truck> Trucks => Set<Truck>();
+
+    public DbSet<Wheel> Wheels => Set<Wheel>();
+    public DbSet<CarbonWheel> CarbonWheels => Set<CarbonWheel>();
+    public DbSet<ChromeWheel> ChromeWheels => Set<ChromeWheel>();
+
+    public DbSet<Engine> Engines => Set<Engine>();
+    public DbSet<GasolineEngine> GasolineEngines => Set<GasolineEngine>();
+    public DbSet<DieselEngine> DieselEngines => Set<DieselEngine>();
+
+    public DbSet<GenericProperty> GenericProperties => Set<GenericProperty>();
+    public DbSet<StringProperty> StringProperties => Set<StringProperty>();
+    public DbSet<NumberProperty> NumberProperties => Set<NumberProperty>();
+
+    protected ResourceInheritanceDbContext(DbContextOptions options)
+        : base(options)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
new file mode 100644
index 0000000000..3842978581
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
@@ -0,0 +1,141 @@
+using Bogus;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using TestBuildingBlocks;
+
+// @formatter:wrap_chained_method_calls chop_always
+// @formatter:keep_existing_linebreaks true
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
+
+internal sealed class ResourceInheritanceFakers : FakerContainer
+{
+    private readonly Lazy<Faker<Bike>> _lazyBikeFaker = new(() =>
+        new Faker<Bike>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(bike => bike.Weight, faker => faker.Random.Decimal(10, 30))
+            .RuleFor(bike => bike.RequiresDriverLicense, _ => false)
+            .RuleFor(bike => bike.GearCount, faker => faker.Random.Int(1, 10)));
+
+    private readonly Lazy<Faker<Tandem>> _lazyTandemFaker = new(() =>
+        new Faker<Tandem>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(tandem => tandem.Weight, faker => faker.Random.Decimal(20, 50))
+            .RuleFor(tandem => tandem.RequiresDriverLicense, _ => false)
+            .RuleFor(tandem => tandem.GearCount, faker => faker.Random.Int(1, 10))
+            .RuleFor(tandem => tandem.PassengerCount, faker => faker.Random.Int(2, 150)));
+
+    private readonly Lazy<Faker<Car>> _lazyCarFaker = new(() =>
+        new Faker<Car>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(car => car.Weight, faker => faker.Random.Decimal(1200, 2000))
+            .RuleFor(car => car.RequiresDriverLicense, _ => true)
+            .RuleFor(car => car.LicensePlate, faker => faker.Random.Replace("??-??-##"))
+            .RuleFor(car => car.SeatCount, faker => faker.Random.Int(2, 8)));
+
+    private readonly Lazy<Faker<Truck>> _lazyTruckFaker = new(() =>
+        new Faker<Truck>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(truck => truck.Weight, faker => faker.Random.Decimal(1200, 12_000))
+            .RuleFor(truck => truck.RequiresDriverLicense, _ => true)
+            .RuleFor(truck => truck.LicensePlate, faker => faker.Random.Replace("??-??-##"))
+            .RuleFor(truck => truck.LoadingCapacity, faker => faker.Random.Decimal(500, 25_000)));
+
+    private readonly Lazy<Faker<CarbonWheel>> _lazyCarbonWheelFaker = new(() =>
+        new Faker<CarbonWheel>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(carbonWheel => carbonWheel.Radius, faker => faker.Random.Decimal(50, 100))
+            .RuleFor(carbonWheel => carbonWheel.HasTube, faker => faker.Random.Bool()));
+
+    private readonly Lazy<Faker<ChromeWheel>> _lazyChromeWheelFaker = new(() =>
+        new Faker<ChromeWheel>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(chromeWheel => chromeWheel.Radius, faker => faker.Random.Decimal(50, 100))
+            .RuleFor(chromeWheel => chromeWheel.PaintColor, faker => faker.Internet.Color()));
+
+    private readonly Lazy<Faker<GasolineEngine>> _lazyGasolineEngineFaker = new(() =>
+        new Faker<GasolineEngine>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(gasolineEngine => gasolineEngine.IsHydrocarbonBased, faker => faker.Random.Bool())
+            .RuleFor(gasolineEngine => gasolineEngine.Capacity, faker => faker.Random.Decimal(10, 500))
+            .RuleFor(gasolineEngine => gasolineEngine.SerialCode, faker => faker.Commerce.Ean8())
+            .RuleFor(gasolineEngine => gasolineEngine.Volatility, faker => faker.Random.Decimal(1, 100)));
+
+    private readonly Lazy<Faker<Cylinder>> _lazyCylinderFaker = new(() =>
+        new Faker<Cylinder>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(cylinder => cylinder.SparkPlugCount, faker => faker.Random.Int(1, 5)));
+
+    private readonly Lazy<Faker<DieselEngine>> _lazyDieselEngineFaker = new(() =>
+        new Faker<DieselEngine>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(dieselEngine => dieselEngine.IsHydrocarbonBased, faker => faker.Random.Bool())
+            .RuleFor(dieselEngine => dieselEngine.Capacity, faker => faker.Random.Decimal(10, 500))
+            .RuleFor(dieselEngine => dieselEngine.SerialCode, faker => faker.Commerce.Ean8())
+            .RuleFor(dieselEngine => dieselEngine.Viscosity, faker => faker.Random.Decimal(1, 100)));
+
+    private readonly Lazy<Faker<VehicleManufacturer>> _lazyVehicleManufacturerFaker = new(() =>
+        new Faker<VehicleManufacturer>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(vehicleManufacturer => vehicleManufacturer.Name, faker => faker.Company.CompanyName()));
+
+    private readonly Lazy<Faker<BicycleLight>> _lazyBicycleLightFaker = new(() =>
+        new Faker<BicycleLight>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(bicycleLight => bicycleLight.Color, faker => faker.Internet.Color()));
+
+    private readonly Lazy<Faker<Box>> _lazyBoxFaker = new(() =>
+        new Faker<Box>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(box => box.Width, faker => faker.Random.Decimal(1, 100))
+            .RuleFor(box => box.Height, faker => faker.Random.Decimal(1, 100))
+            .RuleFor(box => box.Depth, faker => faker.Random.Decimal(1, 100)));
+
+    private readonly Lazy<Faker<NavigationSystem>> _lazyNavigationSystemFaker = new(() =>
+        new Faker<NavigationSystem>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(navigationSystem => navigationSystem.ModelType, faker => faker.Commerce.ProductName()));
+
+    private readonly Lazy<Faker<GenericFeature>> _lazyGenericFeatureFaker = new(() =>
+        new Faker<GenericFeature>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(genericFeature => genericFeature.Description, faker => faker.Lorem.Sentence()));
+
+    private readonly Lazy<Faker<StringProperty>> _lazyStringPropertyFaker = new(() =>
+        new Faker<StringProperty>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(stringProperty => stringProperty.Name, faker => faker.Lorem.Word()));
+
+    private readonly Lazy<Faker<StringValue>> _lazyStringValueFaker = new(() =>
+        new Faker<StringValue>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(stringValue => stringValue.Content, faker => faker.Lorem.Text()));
+
+    private readonly Lazy<Faker<NumberProperty>> _lazyNumberPropertyFaker = new(() =>
+        new Faker<NumberProperty>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(numberProperty => numberProperty.Name, faker => faker.Lorem.Word()));
+
+    private readonly Lazy<Faker<NumberValue>> _lazyNumberValueFaker = new(() =>
+        new Faker<NumberValue>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(numberValue => numberValue.Content, faker => faker.Random.Decimal()));
+
+    public Faker<Bike> Bike => _lazyBikeFaker.Value;
+    public Faker<Tandem> Tandem => _lazyTandemFaker.Value;
+    public Faker<Car> Car => _lazyCarFaker.Value;
+    public Faker<Truck> Truck => _lazyTruckFaker.Value;
+    public Faker<CarbonWheel> CarbonWheel => _lazyCarbonWheelFaker.Value;
+    public Faker<ChromeWheel> ChromeWheel => _lazyChromeWheelFaker.Value;
+    public Faker<GasolineEngine> GasolineEngine => _lazyGasolineEngineFaker.Value;
+    public Faker<Cylinder> Cylinder => _lazyCylinderFaker.Value;
+    public Faker<DieselEngine> DieselEngine => _lazyDieselEngineFaker.Value;
+    public Faker<VehicleManufacturer> VehicleManufacturer => _lazyVehicleManufacturerFaker.Value;
+    public Faker<BicycleLight> BicycleLight => _lazyBicycleLightFaker.Value;
+    public Faker<Box> Box => _lazyBoxFaker.Value;
+    public Faker<NavigationSystem> NavigationSystem => _lazyNavigationSystemFaker.Value;
+    public Faker<GenericFeature> GenericFeature => _lazyGenericFeatureFaker.Value;
+    public Faker<StringProperty> StringProperty => _lazyStringPropertyFaker.Value;
+    public Faker<StringValue> StringValue => _lazyStringValueFaker.Value;
+    public Faker<NumberProperty> NumberProperty => _lazyNumberPropertyFaker.Value;
+    public Faker<NumberValue> NumberValue => _lazyNumberValueFaker.Value;
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
new file mode 100644
index 0000000000..0ce9478b26
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
@@ -0,0 +1,583 @@
+using System.Net;
+using FluentAssertions;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Serialization.Objects;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using Microsoft.Extensions.DependencyInjection;
+using TestBuildingBlocks;
+using Xunit;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
+
+public abstract class ResourceInheritanceTests<TDbContext> : IClassFixture<IntegrationTestContext<TestableStartup<TDbContext>, TDbContext>>
+    where TDbContext : ResourceInheritanceDbContext
+{
+    private readonly IntegrationTestContext<TestableStartup<TDbContext>, TDbContext> _testContext;
+    private readonly ResourceInheritanceFakers _fakers = new();
+
+    protected ResourceInheritanceTests(IntegrationTestContext<TestableStartup<TDbContext>, TDbContext> testContext)
+    {
+        _testContext = testContext;
+
+        testContext.UseController<VehiclesController>();
+        testContext.UseController<BikesController>();
+        testContext.UseController<TandemsController>();
+        testContext.UseController<MotorVehiclesController>();
+        testContext.UseController<CarsController>();
+        testContext.UseController<TrucksController>();
+
+        testContext.UseController<EnginesController>();
+        testContext.UseController<GasolineEnginesController>();
+        testContext.UseController<DieselEnginesController>();
+
+        testContext.UseController<WheelsController>();
+        testContext.UseController<ChromeWheelsController>();
+        testContext.UseController<CarbonWheelsController>();
+
+        var options = (JsonApiOptions)testContext.Factory.Services.GetRequiredService<IJsonApiOptions>();
+        options.UseRelativeLinks = true;
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_abstract_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem, car, truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "bikes").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(bike.StringId);
+
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/bikes/{bike.StringId}");
+
+            resource.Attributes.ShouldHaveCount(3);
+            resource.Attributes.ShouldContainKey("weight").With(value => value.Should().Be(bike.Weight));
+            resource.Attributes.ShouldContainKey("requiresDriverLicense").With(value => value.Should().Be(bike.RequiresDriverLicense));
+            resource.Attributes.ShouldContainKey("gearCount").With(value => value.Should().Be(bike.GearCount));
+
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights");
+
+            foreach ((string? name, RelationshipObject? value) in resource.Relationships)
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/bikes/{bike.StringId}/relationships/{name}");
+                value.Links.Related.Should().Be($"/bikes/{bike.StringId}/{name}");
+            }
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(tandem.StringId);
+
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/tandems/{tandem.StringId}");
+
+            resource.Attributes.ShouldHaveCount(4);
+            resource.Attributes.ShouldContainKey("weight").With(value => value.Should().Be(tandem.Weight));
+            resource.Attributes.ShouldContainKey("requiresDriverLicense").With(value => value.Should().Be(tandem.RequiresDriverLicense));
+            resource.Attributes.ShouldContainKey("gearCount").With(value => value.Should().Be(tandem.GearCount));
+            resource.Attributes.ShouldContainKey("passengerCount").With(value => value.Should().Be(tandem.PassengerCount));
+
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights", "features");
+
+            foreach ((string? name, RelationshipObject? value) in resource.Relationships)
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/tandems/{tandem.StringId}/relationships/{name}");
+                value.Links.Related.Should().Be($"/tandems/{tandem.StringId}/{name}");
+            }
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "cars").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(car.StringId);
+
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/cars/{car.StringId}");
+
+            resource.Attributes.ShouldHaveCount(4);
+            resource.Attributes.ShouldContainKey("weight").With(value => value.Should().Be(car.Weight));
+            resource.Attributes.ShouldContainKey("requiresDriverLicense").With(value => value.Should().Be(car.RequiresDriverLicense));
+            resource.Attributes.ShouldContainKey("licensePlate").With(value => value.Should().Be(car.LicensePlate));
+            resource.Attributes.ShouldContainKey("seatCount").With(value => value.Should().Be(car.SeatCount));
+
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "engine", "navigationSystem", "features");
+
+            foreach ((string? name, RelationshipObject? value) in resource.Relationships)
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/cars/{car.StringId}/relationships/{name}");
+                value.Links.Related.Should().Be($"/cars/{car.StringId}/{name}");
+            }
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "trucks").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(truck.StringId);
+
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/trucks/{truck.StringId}");
+
+            resource.Attributes.ShouldHaveCount(4);
+            resource.Attributes.ShouldContainKey("weight").With(value => value.Should().Be(truck.Weight));
+            resource.Attributes.ShouldContainKey("requiresDriverLicense").With(value => value.Should().Be(truck.RequiresDriverLicense));
+            resource.Attributes.ShouldContainKey("licensePlate").With(value => value.Should().Be(truck.LicensePlate));
+            resource.Attributes.ShouldContainKey("loadingCapacity").With(value => value.Should().Be(truck.LoadingCapacity));
+
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "engine", "navigationSystem", "sleepingArea", "features");
+
+            foreach ((string? name, RelationshipObject? value) in resource.Relationships)
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/trucks/{truck.StringId}/relationships/{name}");
+                value.Links.Related.Should().Be($"/trucks/{truck.StringId}/{name}");
+            }
+        });
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/bikes";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(2);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "bikes").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(bike.StringId);
+
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/bikes/{bike.StringId}");
+
+            resource.Attributes.ShouldHaveCount(3);
+            resource.Attributes.ShouldContainKey("weight").With(value => value.Should().Be(bike.Weight));
+            resource.Attributes.ShouldContainKey("requiresDriverLicense").With(value => value.Should().Be(bike.RequiresDriverLicense));
+            resource.Attributes.ShouldContainKey("gearCount").With(value => value.Should().Be(bike.GearCount));
+
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights");
+
+            foreach ((string? name, RelationshipObject? value) in resource.Relationships)
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/bikes/{bike.StringId}/relationships/{name}");
+                value.Links.Related.Should().Be($"/bikes/{bike.StringId}/{name}");
+            }
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(tandem.StringId);
+
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/tandems/{tandem.StringId}");
+
+            resource.Attributes.ShouldHaveCount(4);
+            resource.Attributes.ShouldContainKey("weight").With(value => value.Should().Be(tandem.Weight));
+            resource.Attributes.ShouldContainKey("requiresDriverLicense").With(value => value.Should().Be(tandem.RequiresDriverLicense));
+            resource.Attributes.ShouldContainKey("gearCount").With(value => value.Should().Be(tandem.GearCount));
+            resource.Attributes.ShouldContainKey("passengerCount").With(value => value.Should().Be(tandem.PassengerCount));
+
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights", "features");
+
+            foreach ((string? name, RelationshipObject? value) in resource.Relationships)
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/tandems/{tandem.StringId}/relationships/{name}");
+                value.Links.Related.Should().Be($"/tandems/{tandem.StringId}/{name}");
+            }
+        });
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/tandems";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(1);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(tandem.StringId);
+
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/tandems/{tandem.StringId}");
+
+            resource.Attributes.ShouldHaveCount(4);
+            resource.Attributes.ShouldContainKey("weight").With(value => value.Should().Be(tandem.Weight));
+            resource.Attributes.ShouldContainKey("requiresDriverLicense").With(value => value.Should().Be(tandem.RequiresDriverLicense));
+            resource.Attributes.ShouldContainKey("gearCount").With(value => value.Should().Be(tandem.GearCount));
+            resource.Attributes.ShouldContainKey("passengerCount").With(value => value.Should().Be(tandem.PassengerCount));
+
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights", "features");
+
+            foreach ((string? name, RelationshipObject? value) in resource.Relationships)
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/tandems/{tandem.StringId}/relationships/{name}");
+                value.Links.Related.Should().Be($"/tandems/{tandem.StringId}/{name}");
+            }
+        });
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resource_at_abstract_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{tandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("tandems");
+        responseDocument.Data.SingleValue.Id.Should().Be(tandem.StringId);
+        responseDocument.Data.SingleValue.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "gearCount", "passengerCount");
+        responseDocument.Data.SingleValue.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights", "features");
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resource_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("tandems");
+        responseDocument.Data.SingleValue.Id.Should().Be(tandem.StringId);
+        responseDocument.Data.SingleValue.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "gearCount", "passengerCount");
+        responseDocument.Data.SingleValue.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights", "features");
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resource_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/tandems/{tandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("tandems");
+        responseDocument.Data.SingleValue.Id.Should().Be(tandem.StringId);
+        responseDocument.Data.SingleValue.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "gearCount", "passengerCount");
+        responseDocument.Data.SingleValue.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights", "features");
+    }
+
+    [Fact]
+    public async Task Cannot_get_secondary_resource_defined_in_derived_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{car.StringId}/engine";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'engine'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_get_secondary_resource_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/cars/{car.StringId}/engine";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("gasolineEngines");
+        responseDocument.Data.SingleValue.Id.Should().Be(car.Engine.StringId);
+
+        responseDocument.Data.SingleValue.Links.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Links.Self.Should().Be($"/gasolineEngines/{car.Engine.StringId}");
+
+        responseDocument.Data.SingleValue.Attributes.ShouldHaveCount(4);
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("isHydrocarbonBased").With(value => value.Should().Be(car.Engine.IsHydrocarbonBased));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("capacity").With(value => value.Should().Be(car.Engine.Capacity));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("serialCode").With(value => value.Should().Be(((GasolineEngine)car.Engine).SerialCode));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("volatility").With(value => value.Should().Be(((GasolineEngine)car.Engine).Volatility));
+
+        responseDocument.Data.SingleValue.Relationships.ShouldHaveCount(1);
+
+        responseDocument.Data.SingleValue.Relationships.ShouldContainKey("cylinders").With(value =>
+        {
+            value.ShouldNotBeNull();
+            value.Links.ShouldNotBeNull();
+            value.Links.Self.Should().Be($"/gasolineEngines/{car.Engine.StringId}/relationships/cylinders");
+            value.Links.Related.Should().Be($"/gasolineEngines/{car.Engine.StringId}/cylinders");
+        });
+    }
+
+    [Fact]
+    public async Task Cannot_get_secondary_resources_defined_in_derived_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+        truck.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{truck.StringId}/features";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'features'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_get_secondary_resources_defined_in_derived_type_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}/features";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'bikes' does not contain a relationship named 'features'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_get_secondary_resources_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+        car.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().Concat(_fakers.CarbonWheel.Generate(2)).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/cars/{car.StringId}/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(0).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(1).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(2).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(3).StringId);
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue.Where(value => value.Type == "chromeWheels"))
+        {
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/chromeWheels/{resource.Id}");
+
+            resource.Attributes.ShouldHaveCount(2);
+            resource.Attributes.ShouldContainKey("radius");
+            resource.Attributes.ShouldContainKey("paintColor");
+        }
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue.Where(value => value.Type == "carbonWheels"))
+        {
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/carbonWheels/{resource.Id}");
+
+            resource.Attributes.ShouldHaveCount(2);
+            resource.Attributes.ShouldContainKey("radius");
+            resource.Attributes.ShouldContainKey("hasTube");
+        }
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue)
+        {
+            resource.Relationships.ShouldHaveCount(1);
+
+            resource.Relationships.ShouldContainKey("vehicle").With(value =>
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/{resource.Type}/{resource.Id}/relationships/vehicle");
+                value.Links.Related.Should().Be($"/{resource.Type}/{resource.Id}/vehicle");
+            });
+        }
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyDbContext.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyDbContext.cs
new file mode 100644
index 0000000000..582b995d89
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyDbContext.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerHierarchy;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+public sealed class TablePerHierarchyDbContext : ResourceInheritanceDbContext
+{
+    public TablePerHierarchyDbContext(DbContextOptions<TablePerHierarchyDbContext> options)
+        : base(options)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyTests.cs
new file mode 100644
index 0000000000..5b6a68ad95
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyTests.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using TestBuildingBlocks;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerHierarchy;
+
+[UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
+public sealed class TablePerHierarchyTests : ResourceInheritanceTests<TablePerHierarchyDbContext>
+{
+    public TablePerHierarchyTests(IntegrationTestContext<TestableStartup<TablePerHierarchyDbContext>, TablePerHierarchyDbContext> testContext)
+        : base(testContext)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeDbContext.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeDbContext.cs
new file mode 100644
index 0000000000..a1549e6332
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeDbContext.cs
@@ -0,0 +1,36 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerType;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+public sealed class TablePerTypeDbContext : ResourceInheritanceDbContext
+{
+    public TablePerTypeDbContext(DbContextOptions<TablePerTypeDbContext> options)
+        : base(options)
+    {
+    }
+
+    protected override void OnModelCreating(ModelBuilder builder)
+    {
+        builder.Entity<Vehicle>().ToTable("Vehicles");
+        builder.Entity<Bike>().ToTable("Bikes");
+        builder.Entity<Tandem>().ToTable("Tandems");
+        builder.Entity<MotorVehicle>().ToTable("MotorVehicles");
+        builder.Entity<Car>().ToTable("Cars");
+        builder.Entity<Truck>().ToTable("Trucks");
+
+        builder.Entity<Wheel>().ToTable("Wheels");
+        builder.Entity<CarbonWheel>().ToTable("CarbonWheels");
+        builder.Entity<ChromeWheel>().ToTable("ChromeWheels");
+
+        builder.Entity<Engine>().ToTable("Engines");
+        builder.Entity<GasolineEngine>().ToTable("GasolineEngines");
+        builder.Entity<DieselEngine>().ToTable("DieselEngines");
+
+        builder.Entity<GenericProperty>().ToTable("GenericProperties");
+        builder.Entity<StringProperty>().ToTable("StringProperties");
+        builder.Entity<NumberProperty>().ToTable("NumberProperties");
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeTests.cs
new file mode 100644
index 0000000000..34f7abe19f
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeTests.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using TestBuildingBlocks;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerType;
+
+[UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
+public sealed class TablePerTypeTests : ResourceInheritanceTests<TablePerTypeDbContext>
+{
+    public TablePerTypeTests(IntegrationTestContext<TestableStartup<TablePerTypeDbContext>, TablePerTypeDbContext> testContext)
+        : base(testContext)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeLinkBuilder.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeLinkBuilder.cs
new file mode 100644
index 0000000000..9b48894ae0
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeLinkBuilder.cs
@@ -0,0 +1,25 @@
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+using JsonApiDotNetCore.Serialization.Objects;
+using JsonApiDotNetCore.Serialization.Response;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Serialization.Response;
+
+internal sealed class FakeLinkBuilder : ILinkBuilder
+{
+    public TopLevelLinks? GetTopLevelLinks()
+    {
+        return null;
+    }
+
+    public ResourceLinks? GetResourceLinks(ResourceType resourceType, IIdentifiable resource)
+    {
+        return null;
+    }
+
+    public RelationshipLinks? GetRelationshipLinks(RelationshipAttribute relationship, IIdentifiable leftResource)
+    {
+        return null;
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeMetaBuilder.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeMetaBuilder.cs
new file mode 100644
index 0000000000..e8e890191b
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeMetaBuilder.cs
@@ -0,0 +1,15 @@
+using JsonApiDotNetCore.Serialization.Response;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Serialization.Response;
+
+internal sealed class FakeMetaBuilder : IMetaBuilder
+{
+    public void Add(IReadOnlyDictionary<string, object?> values)
+    {
+    }
+
+    public IDictionary<string, object?>? Build()
+    {
+        return null;
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeRequestQueryStringAccessor.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeRequestQueryStringAccessor.cs
new file mode 100644
index 0000000000..049c79ce42
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeRequestQueryStringAccessor.cs
@@ -0,0 +1,9 @@
+using JsonApiDotNetCore.QueryStrings;
+using Microsoft.AspNetCore.Http;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Serialization.Response;
+
+internal sealed class FakeRequestQueryStringAccessor : IRequestQueryStringAccessor
+{
+    public IQueryCollection Query { get; } = new QueryCollection(0);
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs
new file mode 100644
index 0000000000..17218acb39
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs
@@ -0,0 +1,100 @@
+using System.Collections.Immutable;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Middleware;
+using JsonApiDotNetCore.Queries.Expressions;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Serialization.Response;
+
+internal sealed class FakeResourceDefinitionAccessor : IResourceDefinitionAccessor
+{
+    public IImmutableSet<IncludeElementExpression> OnApplyIncludes(ResourceType resourceType, IImmutableSet<IncludeElementExpression> existingIncludes)
+    {
+        return existingIncludes;
+    }
+
+    public FilterExpression? OnApplyFilter(ResourceType resourceType, FilterExpression? existingFilter)
+    {
+        return existingFilter;
+    }
+
+    public SortExpression? OnApplySort(ResourceType resourceType, SortExpression? existingSort)
+    {
+        return existingSort;
+    }
+
+    public PaginationExpression? OnApplyPagination(ResourceType resourceType, PaginationExpression? existingPagination)
+    {
+        return existingPagination;
+    }
+
+    public SparseFieldSetExpression? OnApplySparseFieldSet(ResourceType resourceType, SparseFieldSetExpression? existingSparseFieldSet)
+    {
+        return existingSparseFieldSet;
+    }
+
+    public object? GetQueryableHandlerForQueryStringParameter(Type resourceClrType, string parameterName)
+    {
+        return null;
+    }
+
+    public IDictionary<string, object?>? GetMeta(ResourceType resourceType, IIdentifiable resourceInstance)
+    {
+        return null;
+    }
+
+    public Task OnPrepareWriteAsync<TResource>(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
+        where TResource : class, IIdentifiable
+    {
+        return Task.CompletedTask;
+    }
+
+    public Task<IIdentifiable?> OnSetToOneRelationshipAsync<TResource>(TResource leftResource, HasOneAttribute hasOneRelationship,
+        IIdentifiable? rightResourceId, WriteOperationKind writeOperation, CancellationToken cancellationToken)
+        where TResource : class, IIdentifiable
+    {
+        return Task.FromResult(rightResourceId);
+    }
+
+    public Task OnSetToManyRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        WriteOperationKind writeOperation, CancellationToken cancellationToken)
+        where TResource : class, IIdentifiable
+    {
+        return Task.CompletedTask;
+    }
+
+    public Task OnAddToRelationshipAsync<TResource, TId>(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        CancellationToken cancellationToken)
+        where TResource : class, IIdentifiable<TId>
+    {
+        return Task.CompletedTask;
+    }
+
+    public Task OnRemoveFromRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        CancellationToken cancellationToken)
+        where TResource : class, IIdentifiable
+    {
+        return Task.CompletedTask;
+    }
+
+    public Task OnWritingAsync<TResource>(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
+        where TResource : class, IIdentifiable
+    {
+        return Task.CompletedTask;
+    }
+
+    public Task OnWriteSucceededAsync<TResource>(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
+        where TResource : class, IIdentifiable
+    {
+        return Task.CompletedTask;
+    }
+
+    public void OnDeserialize(IIdentifiable resource)
+    {
+    }
+
+    public void OnSerialize(IIdentifiable resource)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/IncompleteResourceGraphTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/IncompleteResourceGraphTests.cs
new file mode 100644
index 0000000000..4384d6aaa7
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/IncompleteResourceGraphTests.cs
@@ -0,0 +1,64 @@
+using FluentAssertions;
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.Middleware;
+using JsonApiDotNetCore.Queries;
+using JsonApiDotNetCore.Queries.Internal;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+using JsonApiDotNetCore.Serialization.Response;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Serialization.Response;
+
+public sealed class IncompleteResourceGraphTests
+{
+    [Fact]
+    public void Fails_when_derived_type_is_missing_in_resource_graph()
+    {
+        // Arrange
+        var options = new JsonApiOptions();
+
+        IResourceGraph resourceGraph = new ResourceGraphBuilder(options, NullLoggerFactory.Instance).Add<Fruit, long>().Build();
+
+        var request = new JsonApiRequest
+        {
+            Kind = EndpointKind.Primary,
+            PrimaryResourceType = resourceGraph.GetResourceType<Fruit>()
+        };
+
+        var linkBuilder = new FakeLinkBuilder();
+        var metaBuilder = new FakeMetaBuilder();
+        var resourceDefinitionAccessor = new FakeResourceDefinitionAccessor();
+        var sparseFieldSetCache = new SparseFieldSetCache(Array.Empty<IQueryConstraintProvider>(), resourceDefinitionAccessor);
+        var requestQueryStringAccessor = new FakeRequestQueryStringAccessor();
+        var evaluatedIncludeCache = new EvaluatedIncludeCache();
+
+        var responseModelAdapter = new ResponseModelAdapter(request, options, linkBuilder, metaBuilder, resourceDefinitionAccessor, evaluatedIncludeCache,
+            sparseFieldSetCache, requestQueryStringAccessor);
+
+        var banana = new Banana();
+
+        // Act
+        Action action = () => responseModelAdapter.Convert(banana);
+
+        // Assert
+        action.Should().ThrowExactly<InvalidConfigurationException>().WithMessage($"Type '{typeof(Banana)}' does not exist in the resource graph.");
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    private abstract class Fruit : Identifiable<long>
+    {
+        [Attr]
+        public bool IsRipe { get; set; }
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    private sealed class Banana : Fruit
+    {
+        [Attr]
+        public int Length { get; set; }
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/ResponseModelAdapterTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/ResponseModelAdapterTests.cs
index 79ab5a85cf..d9459f7ec1 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/ResponseModelAdapterTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/ResponseModelAdapterTests.cs
@@ -1,4 +1,3 @@
-using System.Collections.Immutable;
 using System.Text.Json;
 using FluentAssertions;
 using JsonApiDotNetCore.Configuration;
@@ -7,13 +6,9 @@
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Queries.Internal;
 using JsonApiDotNetCore.Queries.Internal.Parsing;
-using JsonApiDotNetCore.QueryStrings;
-using JsonApiDotNetCore.Resources;
-using JsonApiDotNetCore.Resources.Annotations;
 using JsonApiDotNetCore.Serialization.Objects;
 using JsonApiDotNetCore.Serialization.Response;
 using JsonApiDotNetCoreTests.UnitTests.Serialization.Response.Models;
-using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging.Abstractions;
 using TestBuildingBlocks;
 using Xunit;
@@ -582,131 +577,4 @@ private ResponseModelAdapter CreateAdapter(IJsonApiOptions options, string? prim
         return new ResponseModelAdapter(request, options, linkBuilder, metaBuilder, resourceDefinitionAccessor, evaluatedIncludeCache, sparseFieldSetCache,
             requestQueryStringAccessor);
     }
-
-    private sealed class FakeLinkBuilder : ILinkBuilder
-    {
-        public TopLevelLinks? GetTopLevelLinks()
-        {
-            return null;
-        }
-
-        public ResourceLinks? GetResourceLinks(ResourceType resourceType, IIdentifiable resource)
-        {
-            return null;
-        }
-
-        public RelationshipLinks? GetRelationshipLinks(RelationshipAttribute relationship, IIdentifiable leftResource)
-        {
-            return null;
-        }
-    }
-
-    private sealed class FakeMetaBuilder : IMetaBuilder
-    {
-        public void Add(IReadOnlyDictionary<string, object?> values)
-        {
-        }
-
-        public IDictionary<string, object?>? Build()
-        {
-            return null;
-        }
-    }
-
-    private sealed class FakeResourceDefinitionAccessor : IResourceDefinitionAccessor
-    {
-        public IImmutableSet<IncludeElementExpression> OnApplyIncludes(ResourceType resourceType, IImmutableSet<IncludeElementExpression> existingIncludes)
-        {
-            return existingIncludes;
-        }
-
-        public FilterExpression? OnApplyFilter(ResourceType resourceType, FilterExpression? existingFilter)
-        {
-            return existingFilter;
-        }
-
-        public SortExpression? OnApplySort(ResourceType resourceType, SortExpression? existingSort)
-        {
-            return existingSort;
-        }
-
-        public PaginationExpression? OnApplyPagination(ResourceType resourceType, PaginationExpression? existingPagination)
-        {
-            return existingPagination;
-        }
-
-        public SparseFieldSetExpression? OnApplySparseFieldSet(ResourceType resourceType, SparseFieldSetExpression? existingSparseFieldSet)
-        {
-            return existingSparseFieldSet;
-        }
-
-        public object? GetQueryableHandlerForQueryStringParameter(Type resourceClrType, string parameterName)
-        {
-            return null;
-        }
-
-        public IDictionary<string, object?>? GetMeta(ResourceType resourceType, IIdentifiable resourceInstance)
-        {
-            return null;
-        }
-
-        public Task OnPrepareWriteAsync<TResource>(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable
-        {
-            return Task.CompletedTask;
-        }
-
-        public Task<IIdentifiable?> OnSetToOneRelationshipAsync<TResource>(TResource leftResource, HasOneAttribute hasOneRelationship,
-            IIdentifiable? rightResourceId, WriteOperationKind writeOperation, CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable
-        {
-            return Task.FromResult(rightResourceId);
-        }
-
-        public Task OnSetToManyRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
-            WriteOperationKind writeOperation, CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable
-        {
-            return Task.CompletedTask;
-        }
-
-        public Task OnAddToRelationshipAsync<TResource, TId>(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
-            CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable<TId>
-        {
-            return Task.CompletedTask;
-        }
-
-        public Task OnRemoveFromRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
-            CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable
-        {
-            return Task.CompletedTask;
-        }
-
-        public Task OnWritingAsync<TResource>(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable
-        {
-            return Task.CompletedTask;
-        }
-
-        public Task OnWriteSucceededAsync<TResource>(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable
-        {
-            return Task.CompletedTask;
-        }
-
-        public void OnDeserialize(IIdentifiable resource)
-        {
-        }
-
-        public void OnSerialize(IIdentifiable resource)
-        {
-        }
-    }
-
-    private sealed class FakeRequestQueryStringAccessor : IRequestQueryStringAccessor
-    {
-        public IQueryCollection Query { get; } = new QueryCollection(0);
-    }
 }
diff --git a/test/TestBuildingBlocks/DbContextExtensions.cs b/test/TestBuildingBlocks/DbContextExtensions.cs
index 134d1118c8..b570cbf655 100644
--- a/test/TestBuildingBlocks/DbContextExtensions.cs
+++ b/test/TestBuildingBlocks/DbContextExtensions.cs
@@ -24,14 +24,6 @@ public static async Task ClearTablesAsync<TEntity1, TEntity2>(this DbContext dbC
         await ClearTablesAsync(dbContext, typeof(TEntity1), typeof(TEntity2));
     }
 
-    public static async Task ClearTablesAsync<TEntity1, TEntity2, TEntity3>(this DbContext dbContext)
-        where TEntity1 : class
-        where TEntity2 : class
-        where TEntity3 : class
-    {
-        await ClearTablesAsync(dbContext, typeof(TEntity1), typeof(TEntity2), typeof(TEntity3));
-    }
-
     private static async Task ClearTablesAsync(this DbContext dbContext, params Type[] models)
     {
         foreach (Type model in models)
diff --git a/test/TestBuildingBlocks/NullabilityAssertionExtensions.cs b/test/TestBuildingBlocks/NullabilityAssertionExtensions.cs
index 1ef3172446..0627449664 100644
--- a/test/TestBuildingBlocks/NullabilityAssertionExtensions.cs
+++ b/test/TestBuildingBlocks/NullabilityAssertionExtensions.cs
@@ -48,6 +48,13 @@ public static void ShouldHaveCount<T>([SysNotNull] this IEnumerable<T>? subject,
         return subject![expected];
     }
 
+    [CustomAssertion]
+    public static void ShouldOnlyContainKeys<TKey, TValue>([SysNotNull] this IDictionary<TKey, TValue>? subject, params TKey[] expected)
+    {
+        subject.Should().HaveCount(expected.Length);
+        subject.Should().ContainKeys(expected);
+    }
+
     public static void With<T>(this T subject, [InstantHandle] Action<T> continuation)
     {
         continuation(subject);

From da7024c957585bdee5e8897acf56fafb07e3cadc Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Wed, 16 Mar 2022 02:15:58 +0100
Subject: [PATCH 03/19] Resource inheritance: sparse fieldsets

---
 .../Queries/FieldSelection.cs                 |  75 ++++
 .../Queries/FieldSelectors.cs                 |  70 ++++
 .../Queries/IndentingStringWriter.cs          |  41 ++
 .../Internal/Parsing/SparseFieldTypeParser.cs |   4 +-
 .../Queries/Internal/QueryLayerComposer.cs    | 121 +++---
 .../QueryableBuilding/QueryableBuilder.cs     |   9 +-
 .../QueryableBuilding/SelectClauseBuilder.cs  | 138 +++++--
 src/JsonApiDotNetCore/Queries/QueryLayer.cs   |  82 +---
 .../CarCompositeKeyAwareRepository.cs         |   6 +-
 .../ResourceInheritanceTests.cs               | 376 ++++++++++++++++++
 10 files changed, 753 insertions(+), 169 deletions(-)
 create mode 100644 src/JsonApiDotNetCore/Queries/FieldSelection.cs
 create mode 100644 src/JsonApiDotNetCore/Queries/FieldSelectors.cs
 create mode 100644 src/JsonApiDotNetCore/Queries/IndentingStringWriter.cs

diff --git a/src/JsonApiDotNetCore/Queries/FieldSelection.cs b/src/JsonApiDotNetCore/Queries/FieldSelection.cs
new file mode 100644
index 0000000000..8570addf51
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/FieldSelection.cs
@@ -0,0 +1,75 @@
+using System.Text;
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCore.Queries;
+
+/// <summary>
+/// Provides access to sparse fieldsets, per resource type. There's usually just a single resource type, but there can be multiple in case an endpoint
+/// for an abstract resource type returns derived types.
+/// </summary>
+[PublicAPI]
+public sealed class FieldSelection : Dictionary<ResourceType, FieldSelectors>
+{
+    public bool IsEmpty => Values.All(selectors => selectors.IsEmpty);
+
+    public ISet<ResourceType> GetResourceTypes()
+    {
+        return Keys.ToHashSet();
+    }
+
+#pragma warning disable AV1130 // Return type in method signature should be a collection interface instead of a concrete type
+    public FieldSelectors GetOrCreateSelectors(ResourceType resourceType)
+#pragma warning restore AV1130 // Return type in method signature should be a collection interface instead of a concrete type
+    {
+        ArgumentGuard.NotNull(resourceType, nameof(resourceType));
+
+        if (!ContainsKey(resourceType))
+        {
+            this[resourceType] = new FieldSelectors();
+        }
+
+        return this[resourceType];
+    }
+
+    public override string ToString()
+    {
+        var builder = new StringBuilder();
+
+        var writer = new IndentingStringWriter(builder);
+        WriteSelection(writer);
+
+        return builder.ToString();
+    }
+
+    internal void WriteSelection(IndentingStringWriter writer)
+    {
+        using (writer.Indent())
+        {
+            foreach (ResourceType type in GetResourceTypes())
+            {
+                writer.WriteLine($"{nameof(FieldSelectors)}<{type.ClrType.Name}>");
+                WriterSelectors(writer, type);
+            }
+        }
+    }
+
+    private void WriterSelectors(IndentingStringWriter writer, ResourceType type)
+    {
+        using (writer.Indent())
+        {
+            foreach ((ResourceFieldAttribute field, QueryLayer? nextLayer) in GetOrCreateSelectors(type))
+            {
+                if (nextLayer == null)
+                {
+                    writer.WriteLine(field.ToString());
+                }
+                else
+                {
+                    nextLayer.WriteLayer(writer, $"{field.PublicName}: ");
+                }
+            }
+        }
+    }
+}
diff --git a/src/JsonApiDotNetCore/Queries/FieldSelectors.cs b/src/JsonApiDotNetCore/Queries/FieldSelectors.cs
new file mode 100644
index 0000000000..a07b4f0c79
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/FieldSelectors.cs
@@ -0,0 +1,70 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCore.Queries;
+
+/// <summary>
+/// A data structure that contains which fields (attributes and relationships) to retrieve, or empty to retrieve all. In the case of a relationship, it
+/// contains the nested query constraints.
+/// </summary>
+[PublicAPI]
+public sealed class FieldSelectors : Dictionary<ResourceFieldAttribute, QueryLayer?>
+{
+    public bool IsEmpty => !this.Any();
+
+    public bool ContainsReadOnlyAttribute
+    {
+        get
+        {
+            return this.Any(selector => selector.Key is AttrAttribute attribute && attribute.Property.SetMethod == null);
+        }
+    }
+
+    public bool ContainsOnlyRelationships
+    {
+        get
+        {
+            return this.All(selector => selector.Key is RelationshipAttribute);
+        }
+    }
+
+    public bool ContainsField(ResourceFieldAttribute field)
+    {
+        ArgumentGuard.NotNull(field, nameof(field));
+
+        return ContainsKey(field);
+    }
+
+    public void IncludeAttribute(AttrAttribute attribute)
+    {
+        ArgumentGuard.NotNull(attribute, nameof(attribute));
+
+        this[attribute] = null;
+    }
+
+    public void IncludeAttributes(IEnumerable<AttrAttribute> attributes)
+    {
+        ArgumentGuard.NotNull(attributes, nameof(attributes));
+
+        foreach (AttrAttribute attribute in attributes)
+        {
+            this[attribute] = null;
+        }
+    }
+
+    public void IncludeRelationship(RelationshipAttribute relationship, QueryLayer? queryLayer)
+    {
+        ArgumentGuard.NotNull(relationship, nameof(relationship));
+
+        this[relationship] = queryLayer;
+    }
+
+    public void RemoveAttributes()
+    {
+        while (this.Any(pair => pair.Key is AttrAttribute))
+        {
+            ResourceFieldAttribute field = this.First(pair => pair.Key is AttrAttribute).Key;
+            Remove(field);
+        }
+    }
+}
diff --git a/src/JsonApiDotNetCore/Queries/IndentingStringWriter.cs b/src/JsonApiDotNetCore/Queries/IndentingStringWriter.cs
new file mode 100644
index 0000000000..2d5a366c28
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/IndentingStringWriter.cs
@@ -0,0 +1,41 @@
+using System.Text;
+
+namespace JsonApiDotNetCore.Queries;
+
+internal sealed class IndentingStringWriter : IDisposable
+{
+    private readonly StringBuilder _builder;
+
+    private int _indentDepth;
+
+    public IndentingStringWriter(StringBuilder builder)
+    {
+        _builder = builder;
+    }
+
+    public void WriteLine(string? line)
+    {
+        if (_indentDepth > 0)
+        {
+            _builder.Append(new string(' ', _indentDepth * 2));
+        }
+
+        _builder.AppendLine(line);
+    }
+
+    public IndentingStringWriter Indent()
+    {
+        WriteLine("{");
+        _indentDepth++;
+        return this;
+    }
+
+    public void Dispose()
+    {
+        if (_indentDepth > 0)
+        {
+            _indentDepth--;
+            WriteLine("}");
+        }
+    }
+}
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/SparseFieldTypeParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/SparseFieldTypeParser.cs
index e7c96d21d5..b23dfdfea1 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/SparseFieldTypeParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/SparseFieldTypeParser.cs
@@ -37,14 +37,14 @@ private ResourceType ParseSparseFieldTarget()
 
         EatSingleCharacterToken(TokenKind.OpenBracket);
 
-        ResourceType resourceType = ParseResourceName();
+        ResourceType resourceType = ParseResourceType();
 
         EatSingleCharacterToken(TokenKind.CloseBracket);
 
         return resourceType;
     }
 
-    private ResourceType ParseResourceName()
+    private ResourceType ParseResourceType()
     {
         if (TokenStack.TryPop(out Token? token) && token.Kind == TokenKind.Text)
         {
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs
index f7b95c3c86..253e65012c 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs
@@ -167,7 +167,7 @@ private QueryLayer ComposeTopLayer(IEnumerable<ExpressionInScope> constraints, R
             Filter = GetFilter(expressionsInTopScope, resourceType),
             Sort = GetSort(expressionsInTopScope, resourceType),
             Pagination = topPagination,
-            Projection = GetProjectionForSparseAttributeSet(resourceType)
+            Selection = GetSelectionForSparseAttributeSet(resourceType)
         };
     }
 
@@ -203,9 +203,10 @@ private IImmutableSet<IncludeElementExpression> ProcessIncludeSet(IImmutableSet<
 
         foreach (IncludeElementExpression includeElement in includeElementsEvaluated)
         {
-            parentLayer.Projection ??= new Dictionary<ResourceFieldAttribute, QueryLayer?>();
+            parentLayer.Selection ??= new FieldSelection();
+            FieldSelectors selectors = parentLayer.Selection.GetOrCreateSelectors(parentLayer.ResourceType);
 
-            if (!parentLayer.Projection.ContainsKey(includeElement.Relationship))
+            if (!selectors.ContainsField(includeElement.Relationship))
             {
                 var relationshipChain = new List<RelationshipAttribute>(parentRelationshipChain)
                 {
@@ -232,10 +233,10 @@ private IImmutableSet<IncludeElementExpression> ProcessIncludeSet(IImmutableSet<
                     Filter = isToManyRelationship ? GetFilter(expressionsInCurrentScope, resourceType) : null,
                     Sort = isToManyRelationship ? GetSort(expressionsInCurrentScope, resourceType) : null,
                     Pagination = isToManyRelationship ? GetPagination(expressionsInCurrentScope, resourceType) : null,
-                    Projection = GetProjectionForSparseAttributeSet(resourceType)
+                    Selection = GetSelectionForSparseAttributeSet(resourceType)
                 };
 
-                parentLayer.Projection.Add(includeElement.Relationship, child);
+                selectors.IncludeRelationship(includeElement.Relationship, child);
 
                 IImmutableSet<IncludeElementExpression> updatedChildren = ProcessIncludeSet(includeElement.Children, child, relationshipChain, constraints);
 
@@ -278,18 +279,15 @@ public QueryLayer ComposeForGetById<TId>(TId id, ResourceType primaryResourceTyp
 
         if (fieldSelection == TopFieldSelection.OnlyIdAttribute)
         {
-            queryLayer.Projection = new Dictionary<ResourceFieldAttribute, QueryLayer?>
-            {
-                [idAttribute] = null
-            };
+            queryLayer.Selection = new FieldSelection();
+            FieldSelectors selectors = queryLayer.Selection.GetOrCreateSelectors(primaryResourceType);
+            selectors.IncludeAttribute(idAttribute);
         }
-        else if (fieldSelection == TopFieldSelection.WithAllAttributes && queryLayer.Projection != null)
+        else if (fieldSelection == TopFieldSelection.WithAllAttributes && queryLayer.Selection != null)
         {
             // Discard any top-level ?fields[]= or attribute exclusions from resource definition, because we need the full database row.
-            while (queryLayer.Projection.Any(pair => pair.Key is AttrAttribute))
-            {
-                queryLayer.Projection.Remove(queryLayer.Projection.First(pair => pair.Key is AttrAttribute));
-            }
+            FieldSelectors selectors = queryLayer.Selection.GetOrCreateSelectors(primaryResourceType);
+            selectors.RemoveAttributes();
         }
 
         return queryLayer;
@@ -301,17 +299,23 @@ public QueryLayer ComposeSecondaryLayerForRelationship(ResourceType secondaryRes
         ArgumentGuard.NotNull(secondaryResourceType, nameof(secondaryResourceType));
 
         QueryLayer secondaryLayer = ComposeFromConstraints(secondaryResourceType);
-        secondaryLayer.Projection = GetProjectionForRelationship(secondaryResourceType);
+        secondaryLayer.Selection = GetSelectionForRelationship(secondaryResourceType);
         secondaryLayer.Include = null;
 
         return secondaryLayer;
     }
 
-    private IDictionary<ResourceFieldAttribute, QueryLayer?> GetProjectionForRelationship(ResourceType secondaryResourceType)
+#pragma warning disable AV1130 // Return type in method signature should be a collection interface instead of a concrete type
+    private FieldSelection GetSelectionForRelationship(ResourceType secondaryResourceType)
+#pragma warning restore AV1130 // Return type in method signature should be a collection interface instead of a concrete type
     {
+        var selection = new FieldSelection();
+        FieldSelectors selectors = selection.GetOrCreateSelectors(secondaryResourceType);
+
         IImmutableSet<AttrAttribute> secondaryAttributeSet = _sparseFieldSetCache.GetIdAttributeSetForRelationshipQuery(secondaryResourceType);
+        selectors.IncludeAttributes(secondaryAttributeSet);
 
-        return secondaryAttributeSet.ToDictionary(key => (ResourceFieldAttribute)key, _ => (QueryLayer?)null);
+        return selection;
     }
 
     /// <inheritdoc />
@@ -325,12 +329,12 @@ public QueryLayer WrapLayerForSecondaryEndpoint<TId>(QueryLayer secondaryLayer,
         IncludeExpression? innerInclude = secondaryLayer.Include;
         secondaryLayer.Include = null;
 
-        IImmutableSet<AttrAttribute> primaryAttributeSet = _sparseFieldSetCache.GetIdAttributeSetForRelationshipQuery(primaryResourceType);
-
-        Dictionary<ResourceFieldAttribute, QueryLayer?> primaryProjection =
-            primaryAttributeSet.ToDictionary(key => (ResourceFieldAttribute)key, _ => (QueryLayer?)null);
+        var primarySelection = new FieldSelection();
+        FieldSelectors primarySelectors = primarySelection.GetOrCreateSelectors(primaryResourceType);
 
-        primaryProjection[relationship] = secondaryLayer;
+        IImmutableSet<AttrAttribute> primaryAttributeSet = _sparseFieldSetCache.GetIdAttributeSetForRelationshipQuery(primaryResourceType);
+        primarySelectors.IncludeAttributes(primaryAttributeSet);
+        primarySelectors.IncludeRelationship(relationship, secondaryLayer);
 
         FilterExpression? primaryFilter = GetFilter(Array.Empty<QueryExpression>(), primaryResourceType);
         AttrAttribute primaryIdAttribute = GetIdAttribute(primaryResourceType);
@@ -339,7 +343,7 @@ public QueryLayer WrapLayerForSecondaryEndpoint<TId>(QueryLayer secondaryLayer,
         {
             Include = RewriteIncludeForSecondaryEndpoint(innerInclude, relationship),
             Filter = CreateFilterByIds(primaryId.AsArray(), primaryIdAttribute, primaryFilter),
-            Projection = primaryProjection
+            Selection = primarySelection
         };
     }
 
@@ -387,7 +391,7 @@ public QueryLayer ComposeForUpdate<TId>(TId id, ResourceType primaryResourceType
         primaryLayer.Sort = null;
         primaryLayer.Pagination = null;
         primaryLayer.Filter = CreateFilterByIds(id.AsArray(), primaryIdAttribute, primaryLayer.Filter);
-        primaryLayer.Projection = null;
+        primaryLayer.Selection = null;
 
         return primaryLayer;
     }
@@ -423,14 +427,15 @@ public QueryLayer ComposeForGetRelationshipRightIds(RelationshipAttribute relati
         FilterExpression? baseFilter = GetFilter(Array.Empty<QueryExpression>(), relationship.RightType);
         FilterExpression? filter = CreateFilterByIds(typedIds, rightIdAttribute, baseFilter);
 
+        var selection = new FieldSelection();
+        FieldSelectors selectors = selection.GetOrCreateSelectors(relationship.RightType);
+        selectors.IncludeAttribute(rightIdAttribute);
+
         return new QueryLayer(relationship.RightType)
         {
             Include = IncludeExpression.Empty,
             Filter = filter,
-            Projection = new Dictionary<ResourceFieldAttribute, QueryLayer?>
-            {
-                [rightIdAttribute] = null
-            }
+            Selection = selection
         };
     }
 
@@ -447,22 +452,26 @@ public QueryLayer ComposeForHasMany<TId>(HasManyAttribute hasManyRelationship, T
         FilterExpression? leftFilter = CreateFilterByIds(leftId.AsArray(), leftIdAttribute, null);
         FilterExpression? rightFilter = CreateFilterByIds(rightTypedIds, rightIdAttribute, null);
 
+        var secondarySelection = new FieldSelection();
+        FieldSelectors secondarySelectors = secondarySelection.GetOrCreateSelectors(hasManyRelationship.RightType);
+        secondarySelectors.IncludeAttribute(rightIdAttribute);
+
+        QueryLayer secondaryLayer = new(hasManyRelationship.RightType)
+        {
+            Filter = rightFilter,
+            Selection = secondarySelection
+        };
+
+        var primarySelection = new FieldSelection();
+        FieldSelectors primarySelectors = primarySelection.GetOrCreateSelectors(hasManyRelationship.LeftType);
+        primarySelectors.IncludeRelationship(hasManyRelationship, secondaryLayer);
+        primarySelectors.IncludeAttribute(leftIdAttribute);
+
         return new QueryLayer(hasManyRelationship.LeftType)
         {
             Include = new IncludeExpression(ImmutableHashSet.Create(new IncludeElementExpression(hasManyRelationship))),
             Filter = leftFilter,
-            Projection = new Dictionary<ResourceFieldAttribute, QueryLayer?>
-            {
-                [hasManyRelationship] = new(hasManyRelationship.RightType)
-                {
-                    Filter = rightFilter,
-                    Projection = new Dictionary<ResourceFieldAttribute, QueryLayer?>
-                    {
-                        [rightIdAttribute] = null
-                    }
-                },
-                [leftIdAttribute] = null
-            }
+            Selection = primarySelection
         };
     }
 
@@ -518,22 +527,36 @@ protected virtual PaginationExpression GetPagination(IReadOnlyCollection<QueryEx
         return pagination;
     }
 
-    protected virtual IDictionary<ResourceFieldAttribute, QueryLayer?>? GetProjectionForSparseAttributeSet(ResourceType resourceType)
+#pragma warning disable AV1130 // Return type in method signature should be a collection interface instead of a concrete type
+    protected virtual FieldSelection? GetSelectionForSparseAttributeSet(ResourceType resourceType)
+#pragma warning restore AV1130 // Return type in method signature should be a collection interface instead of a concrete type
     {
         ArgumentGuard.NotNull(resourceType, nameof(resourceType));
 
-        IImmutableSet<ResourceFieldAttribute> fieldSet = _sparseFieldSetCache.GetSparseFieldSetForQuery(resourceType);
+        var selection = new FieldSelection();
 
-        if (!fieldSet.Any())
+        HashSet<ResourceType> resourceTypes = resourceType.GetAllConcreteDerivedTypes().ToHashSet();
+        resourceTypes.Add(resourceType);
+
+        foreach (ResourceType nextType in resourceTypes)
         {
-            return null;
-        }
+            IImmutableSet<ResourceFieldAttribute> fieldSet = _sparseFieldSetCache.GetSparseFieldSetForQuery(nextType);
 
-        HashSet<AttrAttribute> attributeSet = fieldSet.OfType<AttrAttribute>().ToHashSet();
-        AttrAttribute idAttribute = GetIdAttribute(resourceType);
-        attributeSet.Add(idAttribute);
+            if (!fieldSet.Any())
+            {
+                continue;
+            }
+
+            HashSet<AttrAttribute> attributeSet = fieldSet.OfType<AttrAttribute>().ToHashSet();
+
+            FieldSelectors selectors = selection.GetOrCreateSelectors(nextType);
+            selectors.IncludeAttributes(attributeSet);
+
+            AttrAttribute idAttribute = GetIdAttribute(nextType);
+            selectors.IncludeAttribute(idAttribute);
+        }
 
-        return attributeSet.ToDictionary(key => (ResourceFieldAttribute)key, _ => (QueryLayer?)null);
+        return selection.IsEmpty ? null : selection;
     }
 
     private static AttrAttribute GetIdAttribute(ResourceType resourceType)
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryableBuilder.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryableBuilder.cs
index 7ce50c02f1..d571ac1dce 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryableBuilder.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryableBuilder.cs
@@ -3,7 +3,6 @@
 using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Resources;
-using JsonApiDotNetCore.Resources.Annotations;
 using Microsoft.EntityFrameworkCore.Metadata;
 
 namespace JsonApiDotNetCore.Queries.Internal.QueryableBuilding;
@@ -67,9 +66,9 @@ public virtual Expression ApplyQuery(QueryLayer layer)
             expression = ApplyPagination(expression, layer.Pagination);
         }
 
-        if (!layer.Projection.IsNullOrEmpty())
+        if (layer.Selection is { IsEmpty: false })
         {
-            expression = ApplyProjection(expression, layer.Projection, layer.ResourceType);
+            expression = ApplySelection(expression, layer.Selection, layer.ResourceType);
         }
 
         return expression;
@@ -107,11 +106,11 @@ protected virtual Expression ApplyPagination(Expression source, PaginationExpres
         return builder.ApplySkipTake(pagination);
     }
 
-    protected virtual Expression ApplyProjection(Expression source, IDictionary<ResourceFieldAttribute, QueryLayer?> projection, ResourceType resourceType)
+    protected virtual Expression ApplySelection(Expression source, FieldSelection selection, ResourceType resourceType)
     {
         using LambdaScope lambdaScope = _lambdaScopeFactory.CreateScope(_elementType);
 
         var builder = new SelectClauseBuilder(source, lambdaScope, _entityModel, _extensionType, _nameFactory, _resourceFactory);
-        return builder.ApplySelect(projection, resourceType);
+        return builder.ApplySelect(selection, resourceType);
     }
 }
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs
index 3931cdc180..e643cc5b3a 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs
@@ -16,6 +16,8 @@ namespace JsonApiDotNetCore.Queries.Internal.QueryableBuilding;
 [PublicAPI]
 public class SelectClauseBuilder : QueryClauseBuilder<object>
 {
+    private static readonly MethodInfo TypeGetTypeMethod = typeof(object).GetMethod("GetType")!;
+    private static readonly MethodInfo TypeOpEqualityMethod = typeof(Type).GetMethod("op_Equality")!;
     private static readonly CollectionConverter CollectionConverter = new();
     private static readonly ConstantExpression NullConstant = Expression.Constant(null);
 
@@ -42,66 +44,111 @@ public SelectClauseBuilder(Expression source, LambdaScope lambdaScope, IModel en
         _resourceFactory = resourceFactory;
     }
 
-    public Expression ApplySelect(IDictionary<ResourceFieldAttribute, QueryLayer?> selectors, ResourceType resourceType)
+    public Expression ApplySelect(FieldSelection selection, ResourceType resourceType)
     {
-        ArgumentGuard.NotNull(selectors, nameof(selectors));
+        ArgumentGuard.NotNull(selection, nameof(selection));
 
-        if (!selectors.Any())
-        {
-            return _source;
-        }
-
-        Expression bodyInitializer = CreateLambdaBodyInitializer(selectors, resourceType, LambdaScope, false);
+        Expression bodyInitializer = CreateLambdaBodyInitializer(selection, resourceType, LambdaScope, false);
 
         LambdaExpression lambda = Expression.Lambda(bodyInitializer, LambdaScope.Parameter);
 
         return SelectExtensionMethodCall(_source, LambdaScope.Parameter.Type, lambda);
     }
 
-    private Expression CreateLambdaBodyInitializer(IDictionary<ResourceFieldAttribute, QueryLayer?> selectors, ResourceType resourceType,
-        LambdaScope lambdaScope, bool lambdaAccessorRequiresTestForNull)
+    private Expression CreateLambdaBodyInitializer(FieldSelection selection, ResourceType resourceType, LambdaScope lambdaScope,
+        bool lambdaAccessorRequiresTestForNull)
     {
-        ICollection<PropertySelector> propertySelectors = ToPropertySelectors(selectors, resourceType, lambdaScope.Accessor.Type);
+        IEntityType entityType = _entityModel.FindEntityType(resourceType.ClrType)!;
+        IEntityType[] concreteEntityTypes = entityType.GetConcreteDerivedTypesInclusive().ToArray();
 
-        MemberBinding[] propertyAssignments =
-            propertySelectors.Select(selector => CreatePropertyAssignment(selector, lambdaScope)).Cast<MemberBinding>().ToArray();
-
-        NewExpression newExpression = _resourceFactory.CreateNewExpression(lambdaScope.Accessor.Type);
-        Expression memberInit = Expression.MemberInit(newExpression, propertyAssignments);
+        Expression bodyInitializer = concreteEntityTypes.Length > 1
+            ? CreateLambdaBodyInitializerForTypeHierarchy(selection, resourceType, concreteEntityTypes, lambdaScope)
+            : CreateLambdaBodyInitializerForSingleType(selection, resourceType, lambdaScope);
 
         if (!lambdaAccessorRequiresTestForNull)
         {
-            return memberInit;
+            return bodyInitializer;
         }
 
-        return TestForNull(lambdaScope.Accessor, memberInit);
+        return TestForNull(lambdaScope.Accessor, bodyInitializer);
     }
 
-    private ICollection<PropertySelector> ToPropertySelectors(IDictionary<ResourceFieldAttribute, QueryLayer?> resourceFieldSelectors,
-        ResourceType resourceType, Type elementType)
+    private Expression CreateLambdaBodyInitializerForTypeHierarchy(FieldSelection selection, ResourceType baseResourceType,
+        IEnumerable<IEntityType> concreteEntityTypes, LambdaScope lambdaScope)
     {
-        var propertySelectors = new Dictionary<PropertyInfo, PropertySelector>();
+        ISet<ResourceType> resourceTypes = selection.GetResourceTypes();
+        Expression rootCondition = lambdaScope.Accessor;
+
+        foreach (IEntityType entityType in concreteEntityTypes)
+        {
+            ResourceType? resourceType = resourceTypes.SingleOrDefault(type => type.ClrType == entityType.ClrType);
 
-        // If a read-only attribute is selected, its calculated value likely depends on another property, so select all properties.
-        bool includesReadOnlyAttribute = resourceFieldSelectors.Any(selector =>
-            selector.Key is AttrAttribute attribute && attribute.Property.SetMethod == null);
+            if (resourceType != null)
+            {
+                FieldSelectors fieldSelectors = selection.GetOrCreateSelectors(resourceType);
 
-        // Only selecting relationships implicitly means to select all attributes too.
-        bool containsOnlyRelationships = resourceFieldSelectors.All(selector => selector.Key is RelationshipAttribute);
+                if (!fieldSelectors.IsEmpty)
+                {
+                    ICollection<PropertySelector> propertySelectors = ToPropertySelectors(fieldSelectors, resourceType, entityType.ClrType);
 
-        if (includesReadOnlyAttribute || containsOnlyRelationships)
-        {
-            IncludeAllProperties(elementType, propertySelectors);
+                    MemberBinding[] propertyAssignments = propertySelectors.Select(selector => CreatePropertyAssignment(selector, lambdaScope))
+                        .Cast<MemberBinding>().ToArray();
+
+                    NewExpression createInstance = _resourceFactory.CreateNewExpression(entityType.ClrType);
+                    MemberInitExpression memberInit = Expression.MemberInit(createInstance, propertyAssignments);
+                    UnaryExpression castToBaseType = Expression.Convert(memberInit, baseResourceType.ClrType);
+
+                    BinaryExpression typeCheck = CreateRuntimeTypeCheck(lambdaScope, entityType.ClrType);
+                    rootCondition = Expression.Condition(typeCheck, castToBaseType, rootCondition);
+                }
+            }
         }
 
-        IncludeFieldSelection(resourceFieldSelectors, propertySelectors);
+        return rootCondition;
+    }
+
+    private static BinaryExpression CreateRuntimeTypeCheck(LambdaScope lambdaScope, Type concreteClrType)
+    {
+        // Emitting "resource.GetType() == typeof(Article)" instead of "resource is Article" so we don't need to check for most-derived
+        // types first. This way, we can fallback to "anything else" at the end without worrying about order.
+
+        Expression concreteTypeConstant = concreteClrType.CreateTupleAccessExpressionForConstant(typeof(Type));
+        MethodCallExpression getTypeCall = Expression.Call(lambdaScope.Accessor, TypeGetTypeMethod);
 
+        return Expression.MakeBinary(ExpressionType.Equal, getTypeCall, concreteTypeConstant, false, TypeOpEqualityMethod);
+    }
+
+    private Expression CreateLambdaBodyInitializerForSingleType(FieldSelection selection, ResourceType resourceType, LambdaScope lambdaScope)
+    {
+        FieldSelectors fieldSelectors = selection.GetOrCreateSelectors(resourceType);
+        ICollection<PropertySelector> propertySelectors = ToPropertySelectors(fieldSelectors, resourceType, lambdaScope.Accessor.Type);
+
+        MemberBinding[] propertyAssignments =
+            propertySelectors.Select(selector => CreatePropertyAssignment(selector, lambdaScope)).Cast<MemberBinding>().ToArray();
+
+        NewExpression createInstance = _resourceFactory.CreateNewExpression(lambdaScope.Accessor.Type);
+        return Expression.MemberInit(createInstance, propertyAssignments);
+    }
+
+    private ICollection<PropertySelector> ToPropertySelectors(FieldSelectors fieldSelectors, ResourceType resourceType, Type elementType)
+    {
+        var propertySelectors = new Dictionary<PropertyInfo, PropertySelector>();
+
+        if (fieldSelectors.ContainsReadOnlyAttribute || fieldSelectors.ContainsOnlyRelationships)
+        {
+            // If a read-only attribute is selected, its calculated value likely depends on another property, so select all properties.
+            // And only selecting relationships implicitly means to select all attributes too.
+
+            IncludeAllAttributes(elementType, propertySelectors);
+        }
+
+        IncludeFields(fieldSelectors, propertySelectors);
         IncludeEagerLoads(resourceType, propertySelectors);
 
         return propertySelectors.Values;
     }
 
-    private void IncludeAllProperties(Type elementType, Dictionary<PropertyInfo, PropertySelector> propertySelectors)
+    private void IncludeAllAttributes(Type elementType, Dictionary<PropertyInfo, PropertySelector> propertySelectors)
     {
         IEntityType entityModel = _entityModel.GetEntityTypes().Single(type => type.ClrType == elementType);
         IEnumerable<IProperty> entityProperties = entityModel.GetProperties().Where(property => !property.IsShadowProperty()).ToArray();
@@ -113,10 +160,9 @@ private void IncludeAllProperties(Type elementType, Dictionary<PropertyInfo, Pro
         }
     }
 
-    private static void IncludeFieldSelection(IDictionary<ResourceFieldAttribute, QueryLayer?> resourceFieldSelectors,
-        Dictionary<PropertyInfo, PropertySelector> propertySelectors)
+    private static void IncludeFields(FieldSelectors fieldSelectors, Dictionary<PropertyInfo, PropertySelector> propertySelectors)
     {
-        foreach ((ResourceFieldAttribute resourceField, QueryLayer? queryLayer) in resourceFieldSelectors)
+        foreach ((ResourceFieldAttribute resourceField, QueryLayer? queryLayer) in fieldSelectors)
         {
             var propertySelector = new PropertySelector(resourceField.Property, queryLayer);
             IncludeWritableProperty(propertySelector, propertySelectors);
@@ -146,21 +192,25 @@ private static void IncludeEagerLoads(ResourceType resourceType, Dictionary<Prop
         }
     }
 
-    private MemberAssignment CreatePropertyAssignment(PropertySelector selector, LambdaScope lambdaScope)
+    private MemberAssignment CreatePropertyAssignment(PropertySelector propertySelector, LambdaScope lambdaScope)
     {
-        MemberExpression propertyAccess = Expression.Property(lambdaScope.Accessor, selector.Property);
+        bool requiresUpCast = !propertySelector.Property.DeclaringType!.IsAssignableFrom(lambdaScope.Accessor.Type);
+
+        MemberExpression propertyAccess = requiresUpCast
+            ? Expression.MakeMemberAccess(Expression.Convert(lambdaScope.Accessor, propertySelector.Property.DeclaringType!), propertySelector.Property)
+            : Expression.Property(lambdaScope.Accessor, propertySelector.Property);
 
         Expression assignmentRightHandSide = propertyAccess;
 
-        if (selector.NextLayer != null)
+        if (propertySelector.NextLayer != null)
         {
             var lambdaScopeFactory = new LambdaScopeFactory(_nameFactory);
 
-            assignmentRightHandSide = CreateAssignmentRightHandSideForLayer(selector.NextLayer, lambdaScope, propertyAccess,
-                selector.Property, lambdaScopeFactory);
+            assignmentRightHandSide = CreateAssignmentRightHandSideForLayer(propertySelector.NextLayer, lambdaScope, propertyAccess, propertySelector.Property,
+                lambdaScopeFactory);
         }
 
-        return Expression.Bind(selector.Property, assignmentRightHandSide);
+        return Expression.Bind(propertySelector.Property, assignmentRightHandSide);
     }
 
     private Expression CreateAssignmentRightHandSideForLayer(QueryLayer layer, LambdaScope outerLambdaScope, MemberExpression propertyAccess,
@@ -174,13 +224,13 @@ private Expression CreateAssignmentRightHandSideForLayer(QueryLayer layer, Lambd
             return CreateCollectionInitializer(outerLambdaScope, selectorPropertyInfo, bodyElementType, layer, lambdaScopeFactory);
         }
 
-        if (layer.Projection.IsNullOrEmpty())
+        if (layer.Selection == null || layer.Selection.IsEmpty)
         {
             return propertyAccess;
         }
 
         using LambdaScope scope = lambdaScopeFactory.CreateScope(bodyElementType, propertyAccess);
-        return CreateLambdaBodyInitializer(layer.Projection, layer.ResourceType, scope, true);
+        return CreateLambdaBodyInitializer(layer.Selection, layer.ResourceType, scope, true);
     }
 
     private Expression CreateCollectionInitializer(LambdaScope lambdaScope, PropertyInfo collectionProperty, Type elementType, QueryLayer layer,
@@ -208,10 +258,10 @@ private static Expression CopyCollectionExtensionMethodCall(Expression source, s
         return Expression.Call(typeof(Enumerable), operationName, elementType.AsArray(), source);
     }
 
-    private Expression SelectExtensionMethodCall(Expression source, Type elementType, Expression selectorBody)
+    private Expression SelectExtensionMethodCall(Expression source, Type elementType, Expression selectBody)
     {
         Type[] typeArguments = ArrayFactory.Create(elementType, elementType);
-        return Expression.Call(_extensionType, "Select", typeArguments, source, selectorBody);
+        return Expression.Call(_extensionType, "Select", typeArguments, source, selectBody);
     }
 
     private sealed class PropertySelector
diff --git a/src/JsonApiDotNetCore/Queries/QueryLayer.cs b/src/JsonApiDotNetCore/Queries/QueryLayer.cs
index be1d657cfe..c460560a33 100644
--- a/src/JsonApiDotNetCore/Queries/QueryLayer.cs
+++ b/src/JsonApiDotNetCore/Queries/QueryLayer.cs
@@ -2,7 +2,6 @@
 using JetBrains.Annotations;
 using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Queries.Expressions;
-using JsonApiDotNetCore.Resources.Annotations;
 
 namespace JsonApiDotNetCore.Queries;
 
@@ -18,7 +17,7 @@ public sealed class QueryLayer
     public FilterExpression? Filter { get; set; }
     public SortExpression? Sort { get; set; }
     public PaginationExpression? Pagination { get; set; }
-    public IDictionary<ResourceFieldAttribute, QueryLayer?>? Projection { get; set; }
+    public FieldSelection? Selection { get; set; }
 
     public QueryLayer(ResourceType resourceType)
     {
@@ -32,92 +31,41 @@ public override string ToString()
         var builder = new StringBuilder();
 
         var writer = new IndentingStringWriter(builder);
-        WriteLayer(writer, this);
+        WriteLayer(writer, null);
 
         return builder.ToString();
     }
 
-    private static void WriteLayer(IndentingStringWriter writer, QueryLayer layer, string? prefix = null)
+    internal void WriteLayer(IndentingStringWriter writer, string? prefix)
     {
-        writer.WriteLine($"{prefix}{nameof(QueryLayer)}<{layer.ResourceType.ClrType.Name}>");
+        writer.WriteLine($"{prefix}{nameof(QueryLayer)}<{ResourceType.ClrType.Name}>");
 
         using (writer.Indent())
         {
-            if (layer.Include != null)
+            if (Include != null)
             {
-                writer.WriteLine($"{nameof(Include)}: {layer.Include}");
+                writer.WriteLine($"{nameof(Include)}: {Include}");
             }
 
-            if (layer.Filter != null)
+            if (Filter != null)
             {
-                writer.WriteLine($"{nameof(Filter)}: {layer.Filter}");
+                writer.WriteLine($"{nameof(Filter)}: {Filter}");
             }
 
-            if (layer.Sort != null)
+            if (Sort != null)
             {
-                writer.WriteLine($"{nameof(Sort)}: {layer.Sort}");
+                writer.WriteLine($"{nameof(Sort)}: {Sort}");
             }
 
-            if (layer.Pagination != null)
+            if (Pagination != null)
             {
-                writer.WriteLine($"{nameof(Pagination)}: {layer.Pagination}");
+                writer.WriteLine($"{nameof(Pagination)}: {Pagination}");
             }
 
-            if (!layer.Projection.IsNullOrEmpty())
+            if (Selection is { IsEmpty: false })
             {
-                writer.WriteLine(nameof(Projection));
-
-                using (writer.Indent())
-                {
-                    foreach ((ResourceFieldAttribute field, QueryLayer? nextLayer) in layer.Projection)
-                    {
-                        if (nextLayer == null)
-                        {
-                            writer.WriteLine(field.ToString());
-                        }
-                        else
-                        {
-                            WriteLayer(writer, nextLayer, $"{field.PublicName}: ");
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    private sealed class IndentingStringWriter : IDisposable
-    {
-        private readonly StringBuilder _builder;
-        private int _indentDepth;
-
-        public IndentingStringWriter(StringBuilder builder)
-        {
-            _builder = builder;
-        }
-
-        public void WriteLine(string? line)
-        {
-            if (_indentDepth > 0)
-            {
-                _builder.Append(new string(' ', _indentDepth * 2));
-            }
-
-            _builder.AppendLine(line);
-        }
-
-        public IndentingStringWriter Indent()
-        {
-            WriteLine("{");
-            _indentDepth++;
-            return this;
-        }
-
-        public void Dispose()
-        {
-            if (_indentDepth > 0)
-            {
-                _indentDepth--;
-                WriteLine("}");
+                writer.WriteLine(nameof(Selection));
+                Selection.WriteSelection(writer);
             }
         }
     }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/CompositeKeys/CarCompositeKeyAwareRepository.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/CompositeKeys/CarCompositeKeyAwareRepository.cs
index 4009f1dd82..989967bc10 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/CompositeKeys/CarCompositeKeyAwareRepository.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/CompositeKeys/CarCompositeKeyAwareRepository.cs
@@ -41,9 +41,11 @@ private void RecursiveRewriteFilterInLayer(QueryLayer queryLayer)
             queryLayer.Sort = (SortExpression?)_writer.Visit(queryLayer.Sort, null);
         }
 
-        if (queryLayer.Projection != null)
+        if (queryLayer.Selection is { IsEmpty: false })
         {
-            foreach (QueryLayer? nextLayer in queryLayer.Projection.Values.Where(layer => layer != null))
+            foreach (QueryLayer? nextLayer in queryLayer.Selection.GetResourceTypes()
+                .Select(resourceType => queryLayer.Selection.GetOrCreateSelectors(resourceType))
+                .SelectMany(selectors => selectors.Select(selector => selector.Value).Where(layer => layer != null)))
             {
                 RecursiveRewriteFilterInLayer(nextLayer!);
             }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
index 0ce9478b26..d4a82cc5fe 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
@@ -580,4 +580,380 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
             });
         }
     }
+
+    [Fact]
+    public async Task Cannot_get_ToOne_relationship_defined_in_derived_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{car.StringId}/relationships/engine";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'engine'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_get_ToOne_relationship_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/cars/{car.StringId}/relationships/engine";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+        responseDocument.Links.Related.Should().Be($"/cars/{car.StringId}/engine");
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("gasolineEngines");
+        responseDocument.Data.SingleValue.Id.Should().Be(car.Engine.StringId);
+        responseDocument.Data.SingleValue.Links.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_get_ToMany_relationship_defined_in_derived_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+        truck.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{truck.StringId}/relationships/features";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'features'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_get_ToMany_relationship_defined_in_derived_type_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}/relationships/features";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'bikes' does not contain a relationship named 'features'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_get_ToMany_relationship_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+        car.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().Concat(_fakers.CarbonWheel.Generate(2)).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/cars/{car.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+        responseDocument.Links.Related.Should().Be($"/cars/{car.StringId}/wheels");
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(0).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(1).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(2).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(3).StringId);
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue)
+        {
+            resource.Links.Should().BeNull();
+        }
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_abstract_endpoint_with_all_sparse_fieldsets()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem, car, truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string bikeFields = "fields[bikes]=weight,gearCount,lights";
+        const string tandemFields = "fields[tandems]=gearCount,passengerCount,cargoBox";
+        const string carFields = "fields[cars]=weight,requiresDriverLicense,seatCount,engine";
+        const string truckFields = "fields[trucks]=loadingCapacity,sleepingArea";
+
+        const string route = $"/vehicles?{bikeFields}&{tandemFields}&{carFields}&{truckFields}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "bikes").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(bike.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("weight", "gearCount");
+            resource.Relationships.ShouldOnlyContainKeys("lights");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(tandem.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("gearCount", "passengerCount");
+            resource.Relationships.ShouldOnlyContainKeys("cargoBox");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "cars").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(car.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "seatCount");
+            resource.Relationships.ShouldOnlyContainKeys("engine");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "trucks").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(truck.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("loadingCapacity");
+            resource.Relationships.ShouldOnlyContainKeys("sleepingArea");
+        });
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_abstract_endpoint_with_some_sparse_fieldsets()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem, car, truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string bikeFields = "fields[bikes]=weight,gearCount,lights";
+        const string carFields = "fields[cars]=weight,requiresDriverLicense,seatCount,engine";
+
+        const string route = $"/vehicles?{bikeFields}&{carFields}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "bikes").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(bike.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("weight", "gearCount");
+            resource.Relationships.ShouldOnlyContainKeys("lights");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(tandem.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "gearCount", "passengerCount");
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "lights", "cargoBox", "features");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "cars").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(car.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "seatCount");
+            resource.Relationships.ShouldOnlyContainKeys("engine");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "trucks").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(truck.StringId);
+            resource.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "licensePlate", "loadingCapacity");
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "engine", "navigationSystem", "sleepingArea", "features");
+        });
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_concrete_base_endpoint_with_all_sparse_fieldsets()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string bikeFields = "fields[bikes]=weight,gearCount,manufacturer,lights";
+        const string tandemFields = "fields[tandems]=passengerCount,cargoBox";
+
+        const string route = $"/bikes?{bikeFields}&{tandemFields}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(2);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "bikes").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(bike.StringId);
+
+            resource.Attributes.ShouldOnlyContainKeys("weight", "gearCount");
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "lights");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(tandem.StringId);
+
+            resource.Attributes.ShouldOnlyContainKeys("passengerCount");
+            resource.Relationships.ShouldOnlyContainKeys("cargoBox");
+        });
+    }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_concrete_base_endpoint_with_some_sparse_fieldsets()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string tandemFields = "fields[tandems]=passengerCount,cargoBox";
+
+        const string route = $"/bikes?{tandemFields}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(2);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "bikes").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(bike.StringId);
+
+            resource.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "gearCount");
+            resource.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights");
+        });
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems").Subject.With(resource =>
+        {
+            resource.Id.Should().Be(tandem.StringId);
+
+            resource.Attributes.ShouldOnlyContainKeys("passengerCount");
+            resource.Relationships.ShouldOnlyContainKeys("cargoBox");
+        });
+    }
 }

From 971bf333c9393f554483b0d92746315137d42fb3 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Wed, 16 Mar 2022 03:33:20 +0100
Subject: [PATCH 04/19] Changed the expression tokenizer to recognize dots in
 field chains

---
 .../Internal/Parsing/QueryExpressionParser.cs | 38 ++++++++++++++++---
 .../Internal/Parsing/QueryTokenizer.cs        |  1 +
 .../Queries/Internal/Parsing/TokenKind.cs     |  1 +
 .../IncludeParseTests.cs                      |  1 +
 .../LegacyFilterParseTests.cs                 |  1 -
 .../SparseFieldSetParseTests.cs               |  2 +-
 6 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryExpressionParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryExpressionParser.cs
index 4dc7230c24..681c1dd8f4 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryExpressionParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryExpressionParser.cs
@@ -1,4 +1,5 @@
 using System.Collections.Immutable;
+using System.Text;
 using JetBrains.Annotations;
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Resources.Annotations;
@@ -31,17 +32,42 @@ protected virtual void Tokenize(string source)
 
     protected ResourceFieldChainExpression ParseFieldChain(FieldChainRequirements chainRequirements, string? alternativeErrorMessage)
     {
-        if (TokenStack.TryPop(out Token? token) && token.Kind == TokenKind.Text)
+        var pathBuilder = new StringBuilder();
+        EatFieldChain(pathBuilder, alternativeErrorMessage);
+
+        IImmutableList<ResourceFieldAttribute> chain = OnResolveFieldChain(pathBuilder.ToString(), chainRequirements);
+
+        if (chain.Any())
         {
-            IImmutableList<ResourceFieldAttribute> chain = OnResolveFieldChain(token.Value!, chainRequirements);
+            return new ResourceFieldChainExpression(chain);
+        }
+
+        throw new QueryParseException(alternativeErrorMessage ?? "Field name expected.");
+    }
 
-            if (chain.Any())
+    private void EatFieldChain(StringBuilder pathBuilder, string? alternativeErrorMessage)
+    {
+        while (true)
+        {
+            if (TokenStack.TryPop(out Token? token) && token.Kind == TokenKind.Text)
+            {
+                pathBuilder.Append(token.Value);
+
+                if (TokenStack.TryPeek(out Token? nextToken) && nextToken.Kind == TokenKind.Period)
+                {
+                    EatSingleCharacterToken(TokenKind.Period);
+                    pathBuilder.Append('.');
+                }
+                else
+                {
+                    return;
+                }
+            }
+            else
             {
-                return new ResourceFieldChainExpression(chain);
+                throw new QueryParseException(alternativeErrorMessage ?? "Field name expected.");
             }
         }
-
-        throw new QueryParseException(alternativeErrorMessage ?? "Field name expected.");
     }
 
     protected CountExpression? TryParseCount()
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryTokenizer.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryTokenizer.cs
index 6676cae30f..3f04ce92aa 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryTokenizer.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/QueryTokenizer.cs
@@ -14,6 +14,7 @@ public sealed class QueryTokenizer
             [')'] = TokenKind.CloseParen,
             ['['] = TokenKind.OpenBracket,
             [']'] = TokenKind.CloseBracket,
+            ['.'] = TokenKind.Period,
             [','] = TokenKind.Comma,
             [':'] = TokenKind.Colon,
             ['-'] = TokenKind.Minus
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/TokenKind.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/TokenKind.cs
index 75b6952f5a..f73cbd3418 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/TokenKind.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/TokenKind.cs
@@ -6,6 +6,7 @@ public enum TokenKind
     CloseParen,
     OpenBracket,
     CloseBracket,
+    Period,
     Comma,
     Colon,
     Minus,
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs
index 193600ad17..a9ad11a89d 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs
@@ -54,6 +54,7 @@ public void Reader_Is_Enabled(JsonApiQueryStringParameters parametersDisabled, b
     [InlineData("includes", " ", "Unexpected whitespace.")]
     [InlineData("includes", ",", "Relationship name expected.")]
     [InlineData("includes", "posts,", "Relationship name expected.")]
+    [InlineData("includes", "posts.", "Relationship name expected.")]
     [InlineData("includes", "posts[", ", expected.")]
     [InlineData("includes", "title", "Relationship 'title' does not exist on resource type 'blogs'.")]
     [InlineData("includes", "posts.comments.publishTime,",
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/LegacyFilterParseTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/LegacyFilterParseTests.cs
index f09ec08e11..936dcebb7a 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/LegacyFilterParseTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/LegacyFilterParseTests.cs
@@ -31,7 +31,6 @@ public LegacyFilterParseTests()
     [InlineData("filter", "some", "Expected field name between brackets in filter parameter name.")]
     [InlineData("filter[", "some", "Expected field name between brackets in filter parameter name.")]
     [InlineData("filter[]", "some", "Expected field name between brackets in filter parameter name.")]
-    [InlineData("filter[.]", "some", "Relationship '' in '.' does not exist on resource type 'blogPosts'.")]
     [InlineData("filter[some]", "other", "Field 'some' does not exist on resource type 'blogPosts'.")]
     [InlineData("filter[author]", "some", "Attribute 'author' does not exist on resource type 'blogPosts'.")]
     [InlineData("filter[author.posts]", "some",
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SparseFieldSetParseTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SparseFieldSetParseTests.cs
index 6257329e8d..c0b78a7be4 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SparseFieldSetParseTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SparseFieldSetParseTests.cs
@@ -58,7 +58,7 @@ public void Reader_Is_Enabled(JsonApiQueryStringParameters parametersDisabled, b
     [InlineData("fields[]", "", "Resource type expected.")]
     [InlineData("fields[ ]", "", "Unexpected whitespace.")]
     [InlineData("fields[owner]", "", "Resource type 'owner' does not exist.")]
-    [InlineData("fields[owner.posts]", "id", "Resource type 'owner.posts' does not exist.")]
+    [InlineData("fields[owner.posts]", "id", "Resource type 'owner' does not exist.")]
     [InlineData("fields[blogPosts]", " ", "Unexpected whitespace.")]
     [InlineData("fields[blogPosts]", "some", "Field 'some' does not exist on resource type 'blogPosts'.")]
     [InlineData("fields[blogPosts]", "id,owner.name", "Field 'owner.name' does not exist on resource type 'blogPosts'.")]

From 4fc8fa99f3f905a3dbe2d6ae1fe9a1c66eaca16f Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Wed, 16 Mar 2022 16:39:20 +0100
Subject: [PATCH 05/19] Resource inheritance: derived includes

---
 .../ResourceSerializationBenchmarks.cs        |  18 +-
 .../Expressions/IncludeChainConverter.cs      |  72 --
 .../Queries/Internal/Parsing/IncludeParser.cs | 334 ++++++++-
 .../QueryableBuilding/IncludeClauseBuilder.cs |  36 +-
 .../IncludeQueryStringParameterReader.cs      |  17 +-
 .../Response/ResponseModelAdapter.cs          |  17 +-
 .../IntegrationTests/QueryStrings/BlogPost.cs |   3 +
 .../IntegrationTests/QueryStrings/Human.cs    |  22 +
 .../QueryStrings/Includes/IncludeTests.cs     |  22 +
 .../IntegrationTests/QueryStrings/Man.cs      |  21 +
 .../QueryStrings/QueryStringDbContext.cs      |   8 +
 .../QueryStrings/WebAccount.cs                |   3 +
 .../IntegrationTests/QueryStrings/Woman.cs    |  21 +
 .../ResourceInheritanceTests.cs               | 667 ++++++++++++++++++
 .../QueryStringParameters/BaseParseTests.cs   |   3 +
 .../IncludeParseTests.cs                      |  12 +
 16 files changed, 1139 insertions(+), 137 deletions(-)
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Human.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs

diff --git a/benchmarks/Serialization/ResourceSerializationBenchmarks.cs b/benchmarks/Serialization/ResourceSerializationBenchmarks.cs
index 6b716a5401..12f5c2e788 100644
--- a/benchmarks/Serialization/ResourceSerializationBenchmarks.cs
+++ b/benchmarks/Serialization/ResourceSerializationBenchmarks.cs
@@ -127,11 +127,19 @@ protected override IEvaluatedIncludeCache CreateEvaluatedIncludeCache(IResourceG
         RelationshipAttribute multi4 = resourceAType.GetRelationshipByPropertyName(nameof(OutgoingResource.Multi4));
         RelationshipAttribute multi5 = resourceAType.GetRelationshipByPropertyName(nameof(OutgoingResource.Multi5));
 
-        ImmutableArray<ResourceFieldAttribute> chain = ImmutableArray.Create<ResourceFieldAttribute>(single2, single3, multi4, multi5);
-        IEnumerable<ResourceFieldChainExpression> chains = new ResourceFieldChainExpression(chain).AsEnumerable();
-
-        var converter = new IncludeChainConverter();
-        IncludeExpression include = converter.FromRelationshipChains(chains);
+        var include = new IncludeExpression(new HashSet<IncludeElementExpression>
+        {
+            new(single2, new HashSet<IncludeElementExpression>
+            {
+                new(single3, new HashSet<IncludeElementExpression>
+                {
+                    new(multi4, new HashSet<IncludeElementExpression>
+                    {
+                        new(multi5)
+                    }.ToImmutableHashSet())
+                }.ToImmutableHashSet())
+            }.ToImmutableHashSet())
+        }.ToImmutableHashSet());
 
         var cache = new EvaluatedIncludeCache();
         cache.Set(include);
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/IncludeChainConverter.cs b/src/JsonApiDotNetCore/Queries/Expressions/IncludeChainConverter.cs
index edf44e1f14..b35c48efbd 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/IncludeChainConverter.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/IncludeChainConverter.cs
@@ -42,60 +42,6 @@ public IReadOnlyCollection<ResourceFieldChainExpression> GetRelationshipChains(I
         return converter.Chains;
     }
 
-    /// <summary>
-    /// Converts a set of relationship chains into a tree of inclusions.
-    /// </summary>
-    /// <example>
-    /// Input chains: <code><![CDATA[
-    /// Article -> Blog,
-    /// Article -> Revisions -> Author
-    /// ]]></code> Output tree:
-    /// <code><![CDATA[
-    /// Article
-    /// {
-    ///   Blog,
-    ///   Revisions
-    ///   {
-    ///     Author
-    ///   }
-    /// }
-    /// ]]></code>
-    /// </example>
-    public IncludeExpression FromRelationshipChains(IEnumerable<ResourceFieldChainExpression> chains)
-    {
-        ArgumentGuard.NotNull(chains, nameof(chains));
-
-        IImmutableSet<IncludeElementExpression> elements = ConvertChainsToElements(chains);
-        return elements.Any() ? new IncludeExpression(elements) : IncludeExpression.Empty;
-    }
-
-    private static IImmutableSet<IncludeElementExpression> ConvertChainsToElements(IEnumerable<ResourceFieldChainExpression> chains)
-    {
-        var rootNode = new MutableIncludeNode(null!);
-
-        foreach (ResourceFieldChainExpression chain in chains)
-        {
-            ConvertChainToElement(chain, rootNode);
-        }
-
-        return rootNode.Children.Values.Select(child => child.ToExpression()).ToImmutableHashSet();
-    }
-
-    private static void ConvertChainToElement(ResourceFieldChainExpression chain, MutableIncludeNode rootNode)
-    {
-        MutableIncludeNode currentNode = rootNode;
-
-        foreach (RelationshipAttribute relationship in chain.Fields.OfType<RelationshipAttribute>())
-        {
-            if (!currentNode.Children.ContainsKey(relationship))
-            {
-                currentNode.Children[relationship] = new MutableIncludeNode(relationship);
-            }
-
-            currentNode = currentNode.Children[relationship];
-        }
-    }
-
     private sealed class IncludeToChainsConverter : QueryExpressionVisitor<object?, object?>
     {
         private readonly Stack<RelationshipAttribute> _parentRelationshipStack = new();
@@ -144,22 +90,4 @@ private void FlushChain(IncludeElementExpression expression)
             Chains.Add(new ResourceFieldChainExpression(chainBuilder.ToImmutable()));
         }
     }
-
-    private sealed class MutableIncludeNode
-    {
-        private readonly RelationshipAttribute _relationship;
-
-        public IDictionary<RelationshipAttribute, MutableIncludeNode> Children { get; } = new Dictionary<RelationshipAttribute, MutableIncludeNode>();
-
-        public MutableIncludeNode(RelationshipAttribute relationship)
-        {
-            _relationship = relationship;
-        }
-
-        public IncludeElementExpression ToExpression()
-        {
-            IImmutableSet<IncludeElementExpression> elementChildren = Children.Values.Select(child => child.ToExpression()).ToImmutableHashSet();
-            return new IncludeElementExpression(_relationship, elementChildren);
-        }
-    }
 }
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
index 95e51dca92..15e9f4bd03 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
@@ -1,6 +1,8 @@
 using System.Collections.Immutable;
+using System.Text;
 using JetBrains.Annotations;
 using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Resources.Annotations;
 
@@ -9,67 +11,343 @@ namespace JsonApiDotNetCore.Queries.Internal.Parsing;
 [PublicAPI]
 public class IncludeParser : QueryExpressionParser
 {
-    private static readonly IncludeChainConverter IncludeChainConverter = new();
-
-    private readonly Action<RelationshipAttribute, ResourceType, string>? _validateSingleRelationshipCallback;
-    private ResourceType? _resourceTypeInScope;
-
-    public IncludeParser(Action<RelationshipAttribute, ResourceType, string>? validateSingleRelationshipCallback = null)
-    {
-        _validateSingleRelationshipCallback = validateSingleRelationshipCallback;
-    }
-
     public IncludeExpression Parse(string source, ResourceType resourceTypeInScope, int? maximumDepth)
     {
         ArgumentGuard.NotNull(resourceTypeInScope, nameof(resourceTypeInScope));
 
-        _resourceTypeInScope = resourceTypeInScope;
-
         Tokenize(source);
 
-        IncludeExpression expression = ParseInclude(maximumDepth);
+        IncludeExpression expression = ParseInclude(resourceTypeInScope, maximumDepth);
 
         AssertTokenStackIsEmpty();
+        ValidateMaximumIncludeDepth(maximumDepth, expression);
 
         return expression;
     }
 
-    protected IncludeExpression ParseInclude(int? maximumDepth)
+    protected IncludeExpression ParseInclude(ResourceType resourceTypeInScope, int? maximumDepth)
     {
-        ResourceFieldChainExpression firstChain = ParseFieldChain(FieldChainRequirements.IsRelationship, "Relationship name expected.");
+        var treeRoot = IncludeTreeNode.CreateRoot(resourceTypeInScope);
 
-        List<ResourceFieldChainExpression> chains = firstChain.AsList();
+        ParseRelationshipChain(treeRoot);
 
         while (TokenStack.Any())
         {
             EatSingleCharacterToken(TokenKind.Comma);
 
-            ResourceFieldChainExpression nextChain = ParseFieldChain(FieldChainRequirements.IsRelationship, "Relationship name expected.");
-            chains.Add(nextChain);
+            ParseRelationshipChain(treeRoot);
         }
 
-        ValidateMaximumIncludeDepth(maximumDepth, chains);
+        return treeRoot.ToExpression();
+    }
+
+    private void ParseRelationshipChain(IncludeTreeNode treeRoot)
+    {
+        // A relationship name usually matches a single relationship, even when overridden in derived types.
+        // But in the following case, two relationships are matched on GET /shoppingBaskets?include=items:
+        //
+        // public abstract class ShoppingBasket : Identifiable<long>
+        // {
+        // }
+        //
+        // public sealed class SilverShoppingBasket : ShoppingBasket
+        // {
+        //     [HasMany]
+        //     public ISet<Article> Items { get; get; }
+        // }
+        //
+        // public sealed class PlatinumShoppingBasket : ShoppingBasket
+        // {
+        //     [HasMany]
+        //     public ISet<Product> Items { get; get; }
+        // }
+        //
+        // Now if the include chain has subsequent relationships, we need to scan both Items relationships for matches,
+        // which is why ParseRelationshipName returns a collection.
+        //
+        // The advantage of this unfolding is we don't require callers to upcast in relationship chains. The downside is
+        // that there's currently no way to include Products without Articles. We could add such optional upcast syntax
+        // in the future, if desired.
+
+        ICollection<IncludeTreeNode> children = ParseRelationshipName(treeRoot.AsList());
+
+        while (TokenStack.TryPeek(out Token? nextToken) && nextToken.Kind == TokenKind.Period)
+        {
+            EatSingleCharacterToken(TokenKind.Period);
+
+            children = ParseRelationshipName(children);
+        }
+    }
+
+    private ICollection<IncludeTreeNode> ParseRelationshipName(ICollection<IncludeTreeNode> parents)
+    {
+        if (TokenStack.TryPop(out Token? token) && token.Kind == TokenKind.Text)
+        {
+            return LookupRelationshipName(token.Value!, parents);
+        }
 
-        return IncludeChainConverter.FromRelationshipChains(chains);
+        throw new QueryParseException("Relationship name expected.");
     }
 
-    private static void ValidateMaximumIncludeDepth(int? maximumDepth, IEnumerable<ResourceFieldChainExpression> chains)
+    private ICollection<IncludeTreeNode> LookupRelationshipName(string relationshipName, ICollection<IncludeTreeNode> parents)
+    {
+        List<IncludeTreeNode> children = new();
+        HashSet<RelationshipAttribute> relationshipsFound = new();
+
+        foreach (IncludeTreeNode parent in parents)
+        {
+            // Depending on the left side of the include chain, we may match relationships anywhere in the resource type hierarchy.
+            // This is compensated for when rendering the response, which substitutes relationships on base types with the derived ones.
+            ISet<RelationshipAttribute> relationships = GetRelationshipsInTypeOrDerived(parent.Relationship.RightType, relationshipName);
+
+            if (relationships.Any())
+            {
+                relationshipsFound.AddRange(relationships);
+
+                RelationshipAttribute[] relationshipsToInclude = relationships.Where(relationship => relationship.CanInclude).ToArray();
+                ICollection<IncludeTreeNode> affectedChildren = parent.EnsureChildren(relationshipsToInclude);
+                children.AddRange(affectedChildren);
+            }
+        }
+
+        AssertRelationshipsFound(relationshipsFound, relationshipName, parents);
+        AssertAtLeastOneCanBeIncluded(relationshipsFound, relationshipName, parents);
+
+        return children;
+    }
+
+    private ISet<RelationshipAttribute> GetRelationshipsInTypeOrDerived(ResourceType resourceType, string relationshipName)
+    {
+        RelationshipAttribute? relationship = resourceType.FindRelationshipByPublicName(relationshipName);
+
+        if (relationship != null)
+        {
+            return relationship.AsHashSet();
+        }
+
+        // Hiding base members using the 'new' keyword instead of 'override' (effectively breaking inheritance) is currently not supported.
+        // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/knowing-when-to-use-override-and-new-keywords
+        HashSet<RelationshipAttribute> relationshipsInDerivedTypes = new();
+
+        foreach (ResourceType derivedType in resourceType.DirectlyDerivedTypes)
+        {
+            ISet<RelationshipAttribute> relationshipsInDerivedType = GetRelationshipsInTypeOrDerived(derivedType, relationshipName);
+            relationshipsInDerivedTypes.AddRange(relationshipsInDerivedType);
+        }
+
+        return relationshipsInDerivedTypes;
+    }
+
+    private static void AssertRelationshipsFound(ISet<RelationshipAttribute> relationshipsFound, string relationshipName, ICollection<IncludeTreeNode> parents)
+    {
+        if (relationshipsFound.Any())
+        {
+            return;
+        }
+
+        var messageBuilder = new StringBuilder();
+        messageBuilder.Append($"Relationship '{relationshipName}'");
+
+        string[] parentPaths = parents.Select(parent => parent.Path).Distinct().Where(path => path != string.Empty).ToArray();
+
+        if (parentPaths.Length > 0)
+        {
+            messageBuilder.Append($" in '{parentPaths[0]}.{relationshipName}'");
+        }
+
+        ResourceType[] parentResourceTypes = parents.Select(parent => parent.Relationship.RightType).Distinct().ToArray();
+
+        if (parentResourceTypes.Length == 1)
+        {
+            messageBuilder.Append($" does not exist on resource type '{parentResourceTypes[0].PublicName}'");
+        }
+        else
+        {
+            string typeNames = string.Join(", ", parentResourceTypes.Select(type => $"'{type.PublicName}'"));
+            messageBuilder.Append($" does not exist on any of the resource types {typeNames}");
+        }
+
+        bool hasDerived = parents.Any(parent => parent.Relationship.RightType.DirectlyDerivedTypes.Count > 0);
+        messageBuilder.Append(hasDerived ? " or any of its derived types." : ".");
+
+        throw new QueryParseException(messageBuilder.ToString());
+    }
+
+    private static void AssertAtLeastOneCanBeIncluded(ISet<RelationshipAttribute> relationshipsFound, string relationshipName,
+        ICollection<IncludeTreeNode> parents)
+    {
+        if (relationshipsFound.All(relationship => !relationship.CanInclude))
+        {
+            string parentPath = parents.First().Path;
+            ResourceType resourceType = relationshipsFound.First().LeftType;
+
+            string message = parentPath == string.Empty
+                ? $"Including the relationship '{relationshipName}' on '{resourceType}' is not allowed."
+                : $"Including the relationship '{relationshipName}' in '{parentPath}.{relationshipName}' on '{resourceType}' is not allowed.";
+
+            throw new InvalidQueryStringParameterException("include", "Including the requested relationship is not allowed.", message);
+        }
+    }
+
+    private static void ValidateMaximumIncludeDepth(int? maximumDepth, IncludeExpression include)
     {
         if (maximumDepth != null)
         {
-            foreach (ResourceFieldChainExpression chain in chains)
+            Stack<RelationshipAttribute> parentChain = new();
+
+            foreach (IncludeElementExpression element in include.Elements)
             {
-                if (chain.Fields.Count > maximumDepth)
-                {
-                    string path = string.Join('.', chain.Fields.Select(field => field.PublicName));
-                    throw new QueryParseException($"Including '{path}' exceeds the maximum inclusion depth of {maximumDepth}.");
-                }
+                ThrowIfMaximumDepthExceeded(element, parentChain, maximumDepth.Value);
             }
         }
     }
 
+    private static void ThrowIfMaximumDepthExceeded(IncludeElementExpression includeElement, Stack<RelationshipAttribute> parentChain, int maximumDepth)
+    {
+        parentChain.Push(includeElement.Relationship);
+
+        if (parentChain.Count > maximumDepth)
+        {
+            string path = string.Join('.', parentChain.Reverse().Select(relationship => relationship.PublicName));
+            throw new QueryParseException($"Including '{path}' exceeds the maximum inclusion depth of {maximumDepth}.");
+        }
+
+        foreach (IncludeElementExpression child in includeElement.Children)
+        {
+            ThrowIfMaximumDepthExceeded(child, parentChain, maximumDepth);
+        }
+
+        parentChain.Pop();
+    }
+
     protected override IImmutableList<ResourceFieldAttribute> OnResolveFieldChain(string path, FieldChainRequirements chainRequirements)
     {
-        return ChainResolver.ResolveRelationshipChain(_resourceTypeInScope!, path, _validateSingleRelationshipCallback);
+        throw new NotSupportedException();
+    }
+
+    private sealed class IncludeTreeNode
+    {
+        private readonly IncludeTreeNode? _parent;
+        private readonly IDictionary<RelationshipAttribute, IncludeTreeNode> _children = new Dictionary<RelationshipAttribute, IncludeTreeNode>();
+
+        public RelationshipAttribute Relationship { get; }
+
+        public string Path
+        {
+            get
+            {
+                var pathBuilder = new StringBuilder();
+                IncludeTreeNode? parent = this;
+
+                while (parent is { Relationship: not HiddenRootRelationship })
+                {
+                    pathBuilder.Insert(0, pathBuilder.Length > 0 ? $"{parent.Relationship.PublicName}." : parent.Relationship.PublicName);
+                    parent = parent._parent;
+                }
+
+                return pathBuilder.ToString();
+            }
+        }
+
+        private IncludeTreeNode(RelationshipAttribute relationship, IncludeTreeNode? parent)
+        {
+            Relationship = relationship;
+            _parent = parent;
+        }
+
+        public static IncludeTreeNode CreateRoot(ResourceType resourceType)
+        {
+            var relationship = new HiddenRootRelationship(resourceType);
+            return new IncludeTreeNode(relationship, null);
+        }
+
+        public ICollection<IncludeTreeNode> EnsureChildren(ICollection<RelationshipAttribute> relationships)
+        {
+            foreach (RelationshipAttribute relationship in relationships)
+            {
+                if (!_children.ContainsKey(relationship))
+                {
+                    var newChild = new IncludeTreeNode(relationship, this);
+                    _children.Add(relationship, newChild);
+                }
+            }
+
+            return _children.Where(pair => relationships.Contains(pair.Key)).Select(pair => pair.Value).ToList();
+        }
+
+        public IncludeExpression ToExpression()
+        {
+            IncludeElementExpression element = ToElementExpression();
+
+            if (element.Relationship is HiddenRootRelationship)
+            {
+                return new IncludeExpression(element.Children);
+            }
+
+            return new IncludeExpression(ImmutableHashSet.Create(element));
+        }
+
+        private IncludeElementExpression ToElementExpression()
+        {
+            IImmutableSet<IncludeElementExpression> elementChildren = _children.Values.Select(child => child.ToElementExpression()).ToImmutableHashSet();
+            return new IncludeElementExpression(Relationship, elementChildren);
+        }
+
+        public override string ToString()
+        {
+            IncludeExpression include = ToExpression();
+
+            IncludeChainConverter includeChainConverter = new();
+            IReadOnlyCollection<ResourceFieldChainExpression> chains = includeChainConverter.GetRelationshipChains(include);
+
+            IEnumerable<ResourceFieldChainExpression> chainsInOrder = InDisplayOrder(chains);
+            return string.Join(",", chainsInOrder.Select(RelationshipChainToString));
+        }
+
+        private static IEnumerable<ResourceFieldChainExpression> InDisplayOrder(IEnumerable<ResourceFieldChainExpression> chains)
+        {
+            return chains.OrderBy(chain => string.Join('.',
+                chain.Fields.OfType<RelationshipAttribute>().Select(relationship => relationship.PublicName + "@" + relationship.LeftType.PublicName)));
+        }
+
+        private static string RelationshipChainToString(ResourceFieldChainExpression chain)
+        {
+            var textBuilder = new StringBuilder();
+
+            ResourceType? parentType = null;
+
+            foreach (RelationshipAttribute relationship in chain.Fields.Cast<RelationshipAttribute>())
+            {
+                if (textBuilder.Length > 0)
+                {
+                    textBuilder.Append('.');
+                }
+
+                if (parentType == null || !parentType.Equals(relationship.LeftType))
+                {
+                    // This is not official syntax at this time, just helpful for debugging the parser.
+                    textBuilder.Append('[');
+                    textBuilder.Append(relationship.LeftType.PublicName);
+                    textBuilder.Append(']');
+                }
+
+                textBuilder.Append(relationship.PublicName);
+
+                parentType = relationship.RightType;
+            }
+
+            return textBuilder.ToString();
+        }
+
+        private sealed class HiddenRootRelationship : RelationshipAttribute
+        {
+            public HiddenRootRelationship(ResourceType rightType)
+            {
+                ArgumentGuard.NotNull(rightType, nameof(rightType));
+
+                RightType = rightType;
+                PublicName = "<<root>>";
+            }
+        }
     }
 }
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/IncludeClauseBuilder.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/IncludeClauseBuilder.cs
index 6384600a58..14c37bb70d 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/IncludeClauseBuilder.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/IncludeClauseBuilder.cs
@@ -37,44 +37,54 @@ public Expression ApplyInclude(IncludeExpression include)
 
     public override Expression VisitInclude(IncludeExpression expression, object? argument)
     {
-        Expression source = ApplyEagerLoads(_source, _resourceType.EagerLoads, null);
+        // De-duplicate chains coming from derived relationships.
+        HashSet<string> propertyPaths = new();
+
+        ApplyEagerLoads(_resourceType.EagerLoads, null, propertyPaths);
 
         foreach (ResourceFieldChainExpression chain in IncludeChainConverter.GetRelationshipChains(expression))
         {
-            source = ProcessRelationshipChain(chain, source);
+            ProcessRelationshipChain(chain, propertyPaths);
         }
 
-        return source;
+        return ToExpression(propertyPaths);
     }
 
-    private Expression ProcessRelationshipChain(ResourceFieldChainExpression chain, Expression source)
+    private void ProcessRelationshipChain(ResourceFieldChainExpression chain, ISet<string> outputPropertyPaths)
     {
         string? path = null;
-        Expression result = source;
 
         foreach (RelationshipAttribute relationship in chain.Fields.Cast<RelationshipAttribute>())
         {
             path = path == null ? relationship.Property.Name : $"{path}.{relationship.Property.Name}";
 
-            result = ApplyEagerLoads(result, relationship.RightType.EagerLoads, path);
+            ApplyEagerLoads(relationship.RightType.EagerLoads, path, outputPropertyPaths);
         }
 
-        return IncludeExtensionMethodCall(result, path!);
+        outputPropertyPaths.Add(path!);
     }
 
-    private Expression ApplyEagerLoads(Expression source, IEnumerable<EagerLoadAttribute> eagerLoads, string? pathPrefix)
+    private void ApplyEagerLoads(IEnumerable<EagerLoadAttribute> eagerLoads, string? pathPrefix, ISet<string> outputPropertyPaths)
     {
-        Expression result = source;
-
         foreach (EagerLoadAttribute eagerLoad in eagerLoads)
         {
             string path = pathPrefix != null ? $"{pathPrefix}.{eagerLoad.Property.Name}" : eagerLoad.Property.Name;
-            result = IncludeExtensionMethodCall(result, path);
+            outputPropertyPaths.Add(path);
+
+            ApplyEagerLoads(eagerLoad.Children, path, outputPropertyPaths);
+        }
+    }
+
+    private Expression ToExpression(HashSet<string> propertyPaths)
+    {
+        Expression source = _source;
 
-            result = ApplyEagerLoads(result, eagerLoad.Children, path);
+        foreach (string propertyPath in propertyPaths)
+        {
+            source = IncludeExtensionMethodCall(source, propertyPath);
         }
 
-        return result;
+        return source;
     }
 
     private Expression IncludeExtensionMethodCall(Expression source, string navigationPropertyPath)
diff --git a/src/JsonApiDotNetCore/QueryStrings/Internal/IncludeQueryStringParameterReader.cs b/src/JsonApiDotNetCore/QueryStrings/Internal/IncludeQueryStringParameterReader.cs
index 51b815c2ef..6c8bfa2934 100644
--- a/src/JsonApiDotNetCore/QueryStrings/Internal/IncludeQueryStringParameterReader.cs
+++ b/src/JsonApiDotNetCore/QueryStrings/Internal/IncludeQueryStringParameterReader.cs
@@ -6,7 +6,6 @@
 using JsonApiDotNetCore.Queries;
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Queries.Internal.Parsing;
-using JsonApiDotNetCore.Resources.Annotations;
 using Microsoft.Extensions.Primitives;
 
 namespace JsonApiDotNetCore.QueryStrings.Internal;
@@ -18,7 +17,6 @@ public class IncludeQueryStringParameterReader : QueryStringParameterReader, IIn
     private readonly IncludeParser _includeParser;
 
     private IncludeExpression? _includeExpression;
-    private string? _lastParameterName;
 
     public bool AllowEmptyValue => false;
 
@@ -28,18 +26,7 @@ public IncludeQueryStringParameterReader(IJsonApiRequest request, IResourceGraph
         ArgumentGuard.NotNull(options, nameof(options));
 
         _options = options;
-        _includeParser = new IncludeParser(ValidateSingleRelationship);
-    }
-
-    protected void ValidateSingleRelationship(RelationshipAttribute relationship, ResourceType resourceType, string path)
-    {
-        if (!relationship.CanInclude)
-        {
-            throw new InvalidQueryStringParameterException(_lastParameterName!, "Including the requested relationship is not allowed.",
-                path == relationship.PublicName
-                    ? $"Including the relationship '{relationship.PublicName}' on '{resourceType.PublicName}' is not allowed."
-                    : $"Including the relationship '{relationship.PublicName}' in '{path}' on '{resourceType.PublicName}' is not allowed.");
-        }
+        _includeParser = new IncludeParser();
     }
 
     /// <inheritdoc />
@@ -59,8 +46,6 @@ public virtual bool CanRead(string parameterName)
     /// <inheritdoc />
     public virtual void Read(string parameterName, StringValues parameterValue)
     {
-        _lastParameterName = parameterName;
-
         try
         {
             _includeExpression = GetInclude(parameterValue);
diff --git a/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs b/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
index 0e1968821f..4045d2c0c0 100644
--- a/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
+++ b/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
@@ -274,14 +274,25 @@ private void TraverseRelationships(IIdentifiable leftResource, ResourceObjectTre
     private void TraverseRelationship(RelationshipAttribute relationship, IIdentifiable leftResource, ResourceObjectTreeNode leftTreeNode,
         IncludeElementExpression includeElement, EndpointKind kind)
     {
-        object? rightValue = relationship.GetValue(leftResource);
+        if (!relationship.LeftType.ClrType.IsAssignableFrom(leftTreeNode.ResourceType.ClrType))
+        {
+            // Skipping over relationship that is declared on another derived type.
+            return;
+        }
+
+        // In case of resource inheritance, prefer the relationship on derived type over the one on base type.
+        RelationshipAttribute effectiveRelationship = !leftTreeNode.ResourceType.Equals(relationship.LeftType)
+            ? leftTreeNode.ResourceType.GetRelationshipByPropertyName(relationship.Property.Name)
+            : relationship;
+
+        object? rightValue = effectiveRelationship.GetValue(leftResource);
         ICollection<IIdentifiable> rightResources = CollectionConverter.ExtractResources(rightValue);
 
-        leftTreeNode.EnsureHasRelationship(relationship);
+        leftTreeNode.EnsureHasRelationship(effectiveRelationship);
 
         foreach (IIdentifiable rightResource in rightResources)
         {
-            TraverseResource(rightResource, relationship.RightType, kind, includeElement.Children, leftTreeNode, relationship);
+            TraverseResource(rightResource, effectiveRelationship.RightType, kind, includeElement.Children, leftTreeNode, effectiveRelationship);
         }
     }
 
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/BlogPost.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/BlogPost.cs
index a5edb3123f..a628cf9355 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/BlogPost.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/BlogPost.cs
@@ -20,6 +20,9 @@ public sealed class BlogPost : Identifiable<int>
     [HasOne]
     public WebAccount? Reviewer { get; set; }
 
+    [HasMany]
+    public ISet<Human> Contributors { get; set; } = new HashSet<Human>();
+
     [HasMany]
     public ISet<Label> Labels { get; set; } = new HashSet<Label>();
 
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Human.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Human.cs
new file mode 100644
index 0000000000..4754f841a8
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Human.cs
@@ -0,0 +1,22 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.QueryStrings;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.QueryStrings")]
+public abstract class Human : Identifiable<int>
+{
+    [Attr]
+    public string Name { get; set; } = null!;
+
+    [HasOne]
+    public Man? Father { get; set; }
+
+    [HasOne]
+    public Woman? Mother { get; set; }
+
+    [HasMany]
+    public ISet<Human> Children { get; set; } = new HashSet<Human>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Includes/IncludeTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Includes/IncludeTests.cs
index 87e79112de..26ee878b01 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Includes/IncludeTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Includes/IncludeTests.cs
@@ -893,6 +893,28 @@ public async Task Cannot_include_relationship_with_blocked_capability()
         error.Source.Parameter.Should().Be("include");
     }
 
+    [Fact]
+    public async Task Cannot_include_relationship_with_nested_blocked_capability()
+    {
+        // Arrange
+        const string route = "/blogs?include=posts.parent";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.BadRequest);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.BadRequest);
+        error.Title.Should().Be("Including the requested relationship is not allowed.");
+        error.Detail.Should().Be("Including the relationship 'parent' in 'posts.parent' on 'blogPosts' is not allowed.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Parameter.Should().Be("include");
+    }
+
     [Fact]
     public async Task Ignores_null_parent_in_nested_include()
     {
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs
new file mode 100644
index 0000000000..c1be948c35
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs
@@ -0,0 +1,21 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.QueryStrings;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.QueryStrings")]
+public sealed class Man : Human
+{
+    [Attr]
+    public bool HasBeard { get; set; }
+
+    [HasOne]
+    public Woman? Wife { get; set; }
+
+    [HasMany]
+    public ISet<Human> Friends { get; set; } = new HashSet<Human>();
+
+    [HasMany]
+    public ISet<Man> SameGenderFriends { get; set; } = new HashSet<Man>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/QueryStringDbContext.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/QueryStringDbContext.cs
index c1ab78e0a3..1e240f8e8d 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/QueryStringDbContext.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/QueryStringDbContext.cs
@@ -13,6 +13,9 @@ public sealed class QueryStringDbContext : DbContext
     public DbSet<Label> Labels => Set<Label>();
     public DbSet<Comment> Comments => Set<Comment>();
     public DbSet<WebAccount> Accounts => Set<WebAccount>();
+    public DbSet<Human> Humans => Set<Human>();
+    public DbSet<Man> Men => Set<Man>();
+    public DbSet<Woman> Women => Set<Woman>();
     public DbSet<AccountPreferences> AccountPreferences => Set<AccountPreferences>();
     public DbSet<LoginAttempt> LoginAttempts => Set<LoginAttempt>();
     public DbSet<Calendar> Calendars => Set<Calendar>();
@@ -28,5 +31,10 @@ protected override void OnModelCreating(ModelBuilder builder)
         builder.Entity<WebAccount>()
             .HasMany(webAccount => webAccount.Posts)
             .WithOne(blogPost => blogPost.Author!);
+
+        builder.Entity<Man>()
+            .HasOne(man => man.Wife)
+            .WithOne(woman => woman.Husband)
+            .HasForeignKey<Man>();
     }
 }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/WebAccount.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/WebAccount.cs
index 785df7c85f..1749184fa4 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/WebAccount.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/WebAccount.cs
@@ -23,6 +23,9 @@ public sealed class WebAccount : Identifiable<int>
     [Attr]
     public string EmailAddress { get; set; } = null!;
 
+    [HasOne]
+    public Human? Person { get; set; }
+
     [HasMany]
     public IList<BlogPost> Posts { get; set; } = new List<BlogPost>();
 
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs
new file mode 100644
index 0000000000..a7e762514a
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs
@@ -0,0 +1,21 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.QueryStrings;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.QueryStrings")]
+public sealed class Woman : Human
+{
+    [Attr]
+    public string MaidenName { get; set; } = null!;
+
+    [HasOne]
+    public Man? Husband { get; set; }
+
+    [HasMany]
+    public ISet<Human> Friends { get; set; } = new HashSet<Human>();
+
+    [HasMany]
+    public ISet<Woman> SameGenderFriends { get; set; } = new HashSet<Woman>();
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
index d4a82cc5fe..f9c2bb0ac7 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
@@ -1,3 +1,4 @@
+using System.Globalization;
 using System.Net;
 using FluentAssertions;
 using JsonApiDotNetCore.Configuration;
@@ -956,4 +957,670 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
             resource.Relationships.ShouldOnlyContainKeys("cargoBox");
         });
     }
+
+    [Fact]
+    public async Task Can_get_primary_resources_at_abstract_endpoint_with_derived_includes()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+        bike.Manufacturer = _fakers.VehicleManufacturer.Generate();
+        bike.Wheels = _fakers.CarbonWheel.Generate(1).Cast<Wheel>().ToHashSet();
+        bike.CargoBox = _fakers.Box.Generate();
+        bike.Lights = _fakers.BicycleLight.Generate(1).ToHashSet();
+
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.Manufacturer = _fakers.VehicleManufacturer.Generate();
+        tandem.Wheels = _fakers.ChromeWheel.Generate(1).Cast<Wheel>().ToHashSet();
+        tandem.CargoBox = _fakers.Box.Generate();
+        tandem.Lights = _fakers.BicycleLight.Generate(1).ToHashSet();
+        tandem.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+        tandem.Features.ElementAt(0).Properties = _fakers.StringProperty.Generate(1).Cast<GenericProperty>().ToHashSet();
+        ((StringProperty)tandem.Features.ElementAt(0).Properties.ElementAt(0)).Value = _fakers.StringValue.Generate();
+
+        Car car = _fakers.Car.Generate();
+        car.Manufacturer = _fakers.VehicleManufacturer.Generate();
+        car.Wheels = _fakers.CarbonWheel.Generate(1).Cast<Wheel>().ToHashSet();
+        car.Engine = _fakers.GasolineEngine.Generate();
+        ((GasolineEngine)car.Engine).Cylinders = _fakers.Cylinder.Generate(1).ToHashSet();
+        car.NavigationSystem = _fakers.NavigationSystem.Generate();
+        car.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+        car.Features.ElementAt(0).Properties = _fakers.NumberProperty.Generate(1).Cast<GenericProperty>().ToHashSet();
+        ((NumberProperty)car.Features.ElementAt(0).Properties.ElementAt(0)).Value = _fakers.NumberValue.Generate();
+
+        Truck truck = _fakers.Truck.Generate();
+        truck.Manufacturer = _fakers.VehicleManufacturer.Generate();
+        truck.Wheels = _fakers.ChromeWheel.Generate(1).Cast<Wheel>().ToHashSet();
+        truck.Engine = _fakers.DieselEngine.Generate();
+        truck.NavigationSystem = _fakers.NavigationSystem.Generate();
+        truck.SleepingArea = _fakers.Box.Generate();
+        truck.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+        truck.Features.ElementAt(0).Properties = _fakers.StringProperty.Generate(1).Cast<GenericProperty>().ToHashSet();
+        ((StringProperty)truck.Features.ElementAt(0).Properties.ElementAt(0)).Value = _fakers.StringValue.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem, car, truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/vehicles?include=manufacturer,wheels,cargoBox,lights,features.properties.value,engine.cylinders,navigationSystem,sleepingArea";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecuteGetAsync<string>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Should().BeJson($@"{{
+  ""links"": {{
+    ""self"": ""{route}"",
+    ""first"": ""{route}""
+  }},
+  ""data"": [
+    {{
+      ""type"": ""bikes"",
+      ""id"": ""{bike.StringId}"",
+      ""attributes"": {{
+        ""requiresDriverLicense"": {bike.RequiresDriverLicense.ToString().ToLowerInvariant()},
+        ""gearCount"": {bike.GearCount},
+        ""weight"": {bike.Weight.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""cargoBox"": {{
+          ""links"": {{
+            ""self"": ""/bikes/{bike.StringId}/relationships/cargoBox"",
+            ""related"": ""/bikes/{bike.StringId}/cargoBox""
+          }},
+          ""data"": {{
+            ""type"": ""boxes"",
+            ""id"": ""{bike.CargoBox.StringId}""
+          }}
+        }},
+        ""lights"": {{
+          ""links"": {{
+            ""self"": ""/bikes/{bike.StringId}/relationships/lights"",
+            ""related"": ""/bikes/{bike.StringId}/lights""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""bicycleLights"",
+              ""id"": ""{bike.Lights.ElementAt(0).StringId}""
+            }}
+          ]
+        }},
+        ""manufacturer"": {{
+          ""links"": {{
+            ""self"": ""/bikes/{bike.StringId}/relationships/manufacturer"",
+            ""related"": ""/bikes/{bike.StringId}/manufacturer""
+          }},
+          ""data"": {{
+            ""type"": ""vehicleManufacturers"",
+            ""id"": ""{bike.Manufacturer.StringId}""
+          }}
+        }},
+        ""wheels"": {{
+          ""links"": {{
+            ""self"": ""/bikes/{bike.StringId}/relationships/wheels"",
+            ""related"": ""/bikes/{bike.StringId}/wheels""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""carbonWheels"",
+              ""id"": ""{bike.Wheels.OfType<CarbonWheel>().ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/bikes/{bike.StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""cars"",
+      ""id"": ""{car.StringId}"",
+      ""attributes"": {{
+        ""seatCount"": {car.SeatCount},
+        ""requiresDriverLicense"": {car.RequiresDriverLicense.ToString().ToLowerInvariant()},
+        ""licensePlate"": ""{car.LicensePlate}"",
+        ""weight"": {car.Weight.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""features"": {{
+          ""links"": {{
+            ""self"": ""/cars/{car.StringId}/relationships/features"",
+            ""related"": ""/cars/{car.StringId}/features""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""genericFeatures"",
+              ""id"": ""{car.Features.ElementAt(0).StringId}""
+            }}
+          ]
+        }},
+        ""engine"": {{
+          ""links"": {{
+            ""self"": ""/cars/{car.StringId}/relationships/engine"",
+            ""related"": ""/cars/{car.StringId}/engine""
+          }},
+          ""data"": {{
+            ""type"": ""gasolineEngines"",
+            ""id"": ""{car.Engine.StringId}""
+          }}
+        }},
+        ""navigationSystem"": {{
+          ""links"": {{
+            ""self"": ""/cars/{car.StringId}/relationships/navigationSystem"",
+            ""related"": ""/cars/{car.StringId}/navigationSystem""
+          }},
+          ""data"": {{
+            ""type"": ""navigationSystems"",
+            ""id"": ""{car.NavigationSystem.StringId}""
+          }}
+        }},
+        ""manufacturer"": {{
+          ""links"": {{
+            ""self"": ""/cars/{car.StringId}/relationships/manufacturer"",
+            ""related"": ""/cars/{car.StringId}/manufacturer""
+          }},
+          ""data"": {{
+            ""type"": ""vehicleManufacturers"",
+            ""id"": ""{car.Manufacturer.StringId}""
+          }}
+        }},
+        ""wheels"": {{
+          ""links"": {{
+            ""self"": ""/cars/{car.StringId}/relationships/wheels"",
+            ""related"": ""/cars/{car.StringId}/wheels""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""carbonWheels"",
+              ""id"": ""{car.Wheels.OfType<CarbonWheel>().ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/cars/{car.StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""tandems"",
+      ""id"": ""{tandem.StringId}"",
+      ""attributes"": {{
+        ""passengerCount"": {tandem.PassengerCount},
+        ""requiresDriverLicense"": {tandem.RequiresDriverLicense.ToString().ToLowerInvariant()},
+        ""gearCount"": {tandem.GearCount},
+        ""weight"": {tandem.Weight.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""features"": {{
+          ""links"": {{
+            ""self"": ""/tandems/{tandem.StringId}/relationships/features"",
+            ""related"": ""/tandems/{tandem.StringId}/features""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""genericFeatures"",
+              ""id"": ""{tandem.Features.ElementAt(0).StringId}""
+            }}
+          ]
+        }},
+        ""cargoBox"": {{
+          ""links"": {{
+            ""self"": ""/tandems/{tandem.StringId}/relationships/cargoBox"",
+            ""related"": ""/tandems/{tandem.StringId}/cargoBox""
+          }},
+          ""data"": {{
+            ""type"": ""boxes"",
+            ""id"": ""{tandem.CargoBox.StringId}""
+          }}
+        }},
+        ""lights"": {{
+          ""links"": {{
+            ""self"": ""/tandems/{tandem.StringId}/relationships/lights"",
+            ""related"": ""/tandems/{tandem.StringId}/lights""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""bicycleLights"",
+              ""id"": ""{tandem.Lights.ElementAt(0).StringId}""
+            }}
+          ]
+        }},
+        ""manufacturer"": {{
+          ""links"": {{
+            ""self"": ""/tandems/{tandem.StringId}/relationships/manufacturer"",
+            ""related"": ""/tandems/{tandem.StringId}/manufacturer""
+          }},
+          ""data"": {{
+            ""type"": ""vehicleManufacturers"",
+            ""id"": ""{tandem.Manufacturer.StringId}""
+          }}
+        }},
+        ""wheels"": {{
+          ""links"": {{
+            ""self"": ""/tandems/{tandem.StringId}/relationships/wheels"",
+            ""related"": ""/tandems/{tandem.StringId}/wheels""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""chromeWheels"",
+              ""id"": ""{tandem.Wheels.ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/tandems/{tandem.StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""trucks"",
+      ""id"": ""{truck.StringId}"",
+      ""attributes"": {{
+        ""loadingCapacity"": {truck.LoadingCapacity.ToString(CultureInfo.InvariantCulture)},
+        ""requiresDriverLicense"": {truck.RequiresDriverLicense.ToString().ToLowerInvariant()},
+        ""licensePlate"": ""{truck.LicensePlate}"",
+        ""weight"": {truck.Weight.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""sleepingArea"": {{
+          ""links"": {{
+            ""self"": ""/trucks/{truck.StringId}/relationships/sleepingArea"",
+            ""related"": ""/trucks/{truck.StringId}/sleepingArea""
+          }},
+          ""data"": {{
+            ""type"": ""boxes"",
+            ""id"": ""{truck.SleepingArea.StringId}""
+          }}
+        }},
+        ""features"": {{
+          ""links"": {{
+            ""self"": ""/trucks/{truck.StringId}/relationships/features"",
+            ""related"": ""/trucks/{truck.StringId}/features""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""genericFeatures"",
+              ""id"": ""{truck.Features.ElementAt(0).StringId}""
+            }}
+          ]
+        }},
+        ""engine"": {{
+          ""links"": {{
+            ""self"": ""/trucks/{truck.StringId}/relationships/engine"",
+            ""related"": ""/trucks/{truck.StringId}/engine""
+          }},
+          ""data"": {{
+            ""type"": ""dieselEngines"",
+            ""id"": ""{truck.Engine.StringId}""
+          }}
+        }},
+        ""navigationSystem"": {{
+          ""links"": {{
+            ""self"": ""/trucks/{truck.StringId}/relationships/navigationSystem"",
+            ""related"": ""/trucks/{truck.StringId}/navigationSystem""
+          }},
+          ""data"": {{
+            ""type"": ""navigationSystems"",
+            ""id"": ""{truck.NavigationSystem.StringId}""
+          }}
+        }},
+        ""manufacturer"": {{
+          ""links"": {{
+            ""self"": ""/trucks/{truck.StringId}/relationships/manufacturer"",
+            ""related"": ""/trucks/{truck.StringId}/manufacturer""
+          }},
+          ""data"": {{
+            ""type"": ""vehicleManufacturers"",
+            ""id"": ""{truck.Manufacturer.StringId}""
+          }}
+        }},
+        ""wheels"": {{
+          ""links"": {{
+            ""self"": ""/trucks/{truck.StringId}/relationships/wheels"",
+            ""related"": ""/trucks/{truck.StringId}/wheels""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""chromeWheels"",
+              ""id"": ""{truck.Wheels.ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/trucks/{truck.StringId}""
+      }}
+    }}
+  ],
+  ""included"": [
+    {{
+      ""type"": ""boxes"",
+      ""id"": ""{bike.CargoBox.StringId}"",
+      ""attributes"": {{
+        ""width"": {bike.CargoBox.Width.ToString(CultureInfo.InvariantCulture)},
+        ""height"": {bike.CargoBox.Height.ToString(CultureInfo.InvariantCulture)},
+        ""depth"": {bike.CargoBox.Depth.ToString(CultureInfo.InvariantCulture)}
+      }}
+    }},
+    {{
+      ""type"": ""bicycleLights"",
+      ""id"": ""{bike.Lights.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""color"": ""{bike.Lights.ElementAt(0).Color}""
+      }}
+    }},
+    {{
+      ""type"": ""vehicleManufacturers"",
+      ""id"": ""{bike.Manufacturer.StringId}"",
+      ""attributes"": {{
+        ""name"": ""{bike.Manufacturer.Name}""
+      }}
+    }},
+    {{
+      ""type"": ""carbonWheels"",
+      ""id"": ""{bike.Wheels.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""hasTube"": {bike.Wheels.Cast<CarbonWheel>().ElementAt(0).HasTube.ToString().ToLowerInvariant()},
+        ""radius"": {bike.Wheels.ElementAt(0).Radius.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""vehicle"": {{
+          ""links"": {{
+            ""self"": ""/carbonWheels/{bike.Wheels.ElementAt(0).StringId}/relationships/vehicle"",
+            ""related"": ""/carbonWheels/{bike.Wheels.ElementAt(0).StringId}/vehicle""
+          }}
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/carbonWheels/{bike.Wheels.ElementAt(0).StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""genericFeatures"",
+      ""id"": ""{car.Features.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""description"": ""{car.Features.ElementAt(0).Description}""
+      }},
+      ""relationships"": {{
+        ""properties"": {{
+          ""data"": [
+            {{
+              ""type"": ""numberProperties"",
+              ""id"": ""{car.Features.ElementAt(0).Properties.ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }}
+    }},
+    {{
+      ""type"": ""numberProperties"",
+      ""id"": ""{car.Features.ElementAt(0).Properties.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""name"": ""{car.Features.ElementAt(0).Properties.ElementAt(0).Name}""
+      }},
+      ""relationships"": {{
+        ""value"": {{
+          ""data"": {{
+            ""type"": ""numberValues"",
+            ""id"": ""{car.Features.ElementAt(0).Properties.OfType<NumberProperty>().ElementAt(0).Value.StringId}""
+          }}
+        }}
+      }}
+    }},
+    {{
+      ""type"": ""numberValues"",
+      ""id"": ""{car.Features.ElementAt(0).Properties.OfType<NumberProperty>().ElementAt(0).Value.StringId}"",
+      ""attributes"": {{
+        ""content"": {car.Features.ElementAt(0).Properties.OfType<NumberProperty>().ElementAt(0).Value.Content.ToString(CultureInfo.InvariantCulture)}
+      }}
+    }},
+    {{
+      ""type"": ""gasolineEngines"",
+      ""id"": ""{car.Engine.StringId}"",
+      ""attributes"": {{
+        ""isHydrocarbonBased"": {car.Engine.IsHydrocarbonBased.ToString().ToLowerInvariant()},
+        ""serialCode"": ""{((GasolineEngine)car.Engine).SerialCode}"",
+        ""volatility"": {((GasolineEngine)car.Engine).Volatility.ToString(CultureInfo.InvariantCulture)},
+        ""capacity"": {car.Engine.Capacity.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""cylinders"": {{
+          ""links"": {{
+            ""self"": ""/gasolineEngines/{car.Engine.StringId}/relationships/cylinders"",
+            ""related"": ""/gasolineEngines/{car.Engine.StringId}/cylinders""
+          }},
+          ""data"": [
+            {{
+              ""type"": ""cylinders"",
+              ""id"": ""{((GasolineEngine)car.Engine).Cylinders.ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/gasolineEngines/{car.Engine.StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""cylinders"",
+      ""id"": ""{((GasolineEngine)car.Engine).Cylinders.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""sparkPlugCount"": {((GasolineEngine)car.Engine).Cylinders.ElementAt(0).SparkPlugCount}
+      }}
+    }},
+    {{
+      ""type"": ""navigationSystems"",
+      ""id"": ""{car.NavigationSystem.StringId}"",
+      ""attributes"": {{
+        ""modelType"": ""{car.NavigationSystem.ModelType}""
+      }}
+    }},
+    {{
+      ""type"": ""vehicleManufacturers"",
+      ""id"": ""{car.Manufacturer.StringId}"",
+      ""attributes"": {{
+        ""name"": ""{car.Manufacturer.Name}""
+      }}
+    }},
+    {{
+      ""type"": ""carbonWheels"",
+      ""id"": ""{car.Wheels.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""hasTube"": {car.Wheels.OfType<CarbonWheel>().ElementAt(0).HasTube.ToString().ToLowerInvariant()},
+        ""radius"": {car.Wheels.ElementAt(0).Radius.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""vehicle"": {{
+          ""links"": {{
+            ""self"": ""/carbonWheels/{car.Wheels.ElementAt(0).StringId}/relationships/vehicle"",
+            ""related"": ""/carbonWheels/{car.Wheels.ElementAt(0).StringId}/vehicle""
+          }}
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/carbonWheels/{car.Wheels.ElementAt(0).StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""genericFeatures"",
+      ""id"": ""{tandem.Features.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""description"": ""{tandem.Features.ElementAt(0).Description}""
+      }},
+      ""relationships"": {{
+        ""properties"": {{
+          ""data"": [
+            {{
+              ""type"": ""stringProperties"",
+              ""id"": ""{tandem.Features.ElementAt(0).Properties.ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }}
+    }},
+    {{
+      ""type"": ""stringProperties"",
+      ""id"": ""{tandem.Features.ElementAt(0).Properties.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""name"": ""{tandem.Features.ElementAt(0).Properties.ElementAt(0).Name}""
+      }},
+      ""relationships"": {{
+        ""value"": {{
+          ""data"": {{
+            ""type"": ""stringValues"",
+            ""id"": ""{tandem.Features.ElementAt(0).Properties.OfType<StringProperty>().ElementAt(0).Value.StringId}""
+          }}
+        }}
+      }}
+    }},
+    {{
+      ""type"": ""stringValues"",
+      ""id"": ""{tandem.Features.ElementAt(0).Properties.OfType<StringProperty>().ElementAt(0).Value.StringId}"",
+      ""attributes"": {{
+        ""content"": ""{tandem.Features.ElementAt(0).Properties.OfType<StringProperty>().ElementAt(0).Value.Content}""
+      }}
+    }},
+    {{
+      ""type"": ""boxes"",
+      ""id"": ""{tandem.CargoBox.StringId}"",
+      ""attributes"": {{
+        ""width"": {tandem.CargoBox.Width.ToString(CultureInfo.InvariantCulture)},
+        ""height"": {tandem.CargoBox.Height.ToString(CultureInfo.InvariantCulture)},
+        ""depth"": {tandem.CargoBox.Depth.ToString(CultureInfo.InvariantCulture)}
+      }}
+    }},
+    {{
+      ""type"": ""bicycleLights"",
+      ""id"": ""{tandem.Lights.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""color"": ""{tandem.Lights.ElementAt(0).Color}""
+      }}
+    }},
+    {{
+      ""type"": ""vehicleManufacturers"",
+      ""id"": ""{tandem.Manufacturer.StringId}"",
+      ""attributes"": {{
+        ""name"": ""{tandem.Manufacturer.Name}""
+      }}
+    }},
+    {{
+      ""type"": ""chromeWheels"",
+      ""id"": ""{tandem.Wheels.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""paintColor"": ""{tandem.Wheels.OfType<ChromeWheel>().ElementAt(0).PaintColor}"",
+        ""radius"": {tandem.Wheels.ElementAt(0).Radius.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""vehicle"": {{
+          ""links"": {{
+            ""self"": ""/chromeWheels/{tandem.Wheels.ElementAt(0).StringId}/relationships/vehicle"",
+            ""related"": ""/chromeWheels/{tandem.Wheels.ElementAt(0).StringId}/vehicle""
+          }}
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/chromeWheels/{tandem.Wheels.ElementAt(0).StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""boxes"",
+      ""id"": ""{truck.SleepingArea.StringId}"",
+      ""attributes"": {{
+        ""width"": {truck.SleepingArea.Width.ToString(CultureInfo.InvariantCulture)},
+        ""height"": {truck.SleepingArea.Height.ToString(CultureInfo.InvariantCulture)},
+        ""depth"": {truck.SleepingArea.Depth.ToString(CultureInfo.InvariantCulture)}
+      }}
+    }},
+    {{
+      ""type"": ""genericFeatures"",
+      ""id"": ""{truck.Features.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""description"": ""{truck.Features.ElementAt(0).Description}""
+      }},
+      ""relationships"": {{
+        ""properties"": {{
+          ""data"": [
+            {{
+              ""type"": ""stringProperties"",
+              ""id"": ""{truck.Features.ElementAt(0).Properties.ElementAt(0).StringId}""
+            }}
+          ]
+        }}
+      }}
+    }},
+    {{
+      ""type"": ""stringProperties"",
+      ""id"": ""{truck.Features.ElementAt(0).Properties.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""name"": ""{truck.Features.ElementAt(0).Properties.ElementAt(0).Name}""
+      }},
+      ""relationships"": {{
+        ""value"": {{
+          ""data"": {{
+            ""type"": ""stringValues"",
+            ""id"": ""{truck.Features.ElementAt(0).Properties.OfType<StringProperty>().ElementAt(0).Value.StringId}""
+          }}
+        }}
+      }}
+    }},
+    {{
+      ""type"": ""stringValues"",
+      ""id"": ""{truck.Features.ElementAt(0).Properties.OfType<StringProperty>().ElementAt(0).Value.StringId}"",
+      ""attributes"": {{
+        ""content"": ""{truck.Features.ElementAt(0).Properties.OfType<StringProperty>().ElementAt(0).Value.Content}""
+      }}
+    }},
+    {{
+      ""type"": ""dieselEngines"",
+      ""id"": ""{truck.Engine.StringId}"",
+      ""attributes"": {{
+        ""isHydrocarbonBased"": {truck.Engine.IsHydrocarbonBased.ToString().ToLowerInvariant()},
+        ""serialCode"": ""{((DieselEngine)truck.Engine).SerialCode}"",
+        ""viscosity"": {((DieselEngine)truck.Engine).Viscosity.ToString(CultureInfo.InvariantCulture)},
+        ""capacity"": {truck.Engine.Capacity.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""links"": {{
+        ""self"": ""/dieselEngines/{truck.Engine.StringId}""
+      }}
+    }},
+    {{
+      ""type"": ""navigationSystems"",
+      ""id"": ""{truck.NavigationSystem.StringId}"",
+      ""attributes"": {{
+        ""modelType"": ""{truck.NavigationSystem.ModelType}""
+      }}
+    }},
+    {{
+      ""type"": ""vehicleManufacturers"",
+      ""id"": ""{truck.Manufacturer.StringId}"",
+      ""attributes"": {{
+        ""name"": ""{truck.Manufacturer.Name}""
+      }}
+    }},
+    {{
+      ""type"": ""chromeWheels"",
+      ""id"": ""{truck.Wheels.ElementAt(0).StringId}"",
+      ""attributes"": {{
+        ""paintColor"": ""{truck.Wheels.OfType<ChromeWheel>().ElementAt(0).PaintColor}"",
+        ""radius"": {truck.Wheels.ElementAt(0).Radius.ToString(CultureInfo.InvariantCulture)}
+      }},
+      ""relationships"": {{
+        ""vehicle"": {{
+          ""links"": {{
+            ""self"": ""/chromeWheels/{truck.Wheels.ElementAt(0).StringId}/relationships/vehicle"",
+            ""related"": ""/chromeWheels/{truck.Wheels.ElementAt(0).StringId}/vehicle""
+          }}
+        }}
+      }},
+      ""links"": {{
+        ""self"": ""/chromeWheels/{truck.Wheels.ElementAt(0).StringId}""
+      }}
+    }}
+  ]
+}}");
+    }
 }
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/BaseParseTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/BaseParseTests.cs
index 273bb6cad8..abb6716b01 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/BaseParseTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/BaseParseTests.cs
@@ -24,6 +24,9 @@ protected BaseParseTests()
             .Add<Label, int>()
             .Add<Comment, int>()
             .Add<WebAccount, int>()
+            .Add<Human, int>()
+            .Add<Man, int>()
+            .Add<Woman, int>()
             .Add<AccountPreferences, int>()
             .Add<LoginAttempt, int>()
             .Build();
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs
index a9ad11a89d..7c7c28f4e3 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/IncludeParseTests.cs
@@ -59,6 +59,12 @@ public void Reader_Is_Enabled(JsonApiQueryStringParameters parametersDisabled, b
     [InlineData("includes", "title", "Relationship 'title' does not exist on resource type 'blogs'.")]
     [InlineData("includes", "posts.comments.publishTime,",
         "Relationship 'publishTime' in 'posts.comments.publishTime' does not exist on resource type 'comments'.")]
+    [InlineData("includes", "owner.person.children.unknown",
+        "Relationship 'unknown' in 'owner.person.children.unknown' does not exist on resource type 'humans' or any of its derived types.")]
+    [InlineData("includes", "owner.person.friends.unknown",
+        "Relationship 'unknown' in 'owner.person.friends.unknown' does not exist on resource type 'humans' or any of its derived types.")]
+    [InlineData("includes", "owner.person.sameGenderFriends.unknown",
+        "Relationship 'unknown' in 'owner.person.sameGenderFriends.unknown' does not exist on any of the resource types 'men', 'women'.")]
     public void Reader_Read_Fails(string parameterName, string parameterValue, string errorMessage)
     {
         // Act
@@ -86,6 +92,12 @@ public void Reader_Read_Fails(string parameterName, string parameterValue, strin
     [InlineData("includes", "posts.comments", "posts.comments")]
     [InlineData("includes", "posts,posts.comments", "posts.comments")]
     [InlineData("includes", "posts,posts.labels,posts.comments", "posts.comments,posts.labels")]
+    [InlineData("includes", "owner.person.children.husband", "owner.person.children.husband")]
+    [InlineData("includes", "owner.person.wife,owner.person.husband", "owner.person.husband,owner.person.wife")]
+    [InlineData("includes", "owner.person.father.children.wife", "owner.person.father.children.wife")]
+    [InlineData("includes", "owner.person.friends", "owner.person.friends,owner.person.friends")]
+    [InlineData("includes", "owner.person.friends.friends",
+        "owner.person.friends.friends,owner.person.friends.friends,owner.person.friends.friends,owner.person.friends.friends")]
     public void Reader_Read_Succeeds(string parameterName, string parameterValue, string valueExpected)
     {
         // Act

From 5fdfa7c325c2cd6ffe0011e92d59da00e275e0c3 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Thu, 17 Mar 2022 11:41:26 +0100
Subject: [PATCH 06/19] Resource inheritance: derived filters

---
 .../Queries/Expressions/IsTypeExpression.cs   |  78 +++++++
 .../Expressions/QueryExpressionRewriter.cs    |  12 ++
 .../Expressions/QueryExpressionVisitor.cs     |   5 +
 .../Queries/Internal/Parsing/FilterParser.cs  | 124 ++++++++++-
 .../Queries/Internal/Parsing/Keywords.cs      |   1 +
 .../Parsing/ResourceFieldChainResolver.cs     |  26 +++
 .../Internal/QueryableBuilding/LambdaScope.cs |  23 +-
 .../QueryableBuilding/LambdaScopeFactory.cs   |   2 +-
 .../QueryableBuilding/QueryClauseBuilder.cs   |  22 +-
 .../QueryableBuilding/SelectClauseBuilder.cs  |   3 +-
 .../QueryableBuilding/WhereClauseBuilder.cs   |  16 ++
 .../ResourceInheritanceTests.cs               | 201 ++++++++++++++++++
 .../QueryStringParameters/FilterParseTests.cs |  13 ++
 13 files changed, 509 insertions(+), 17 deletions(-)
 create mode 100644 src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs

diff --git a/src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs
new file mode 100644
index 0000000000..5277b2b71b
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs
@@ -0,0 +1,78 @@
+using System.Text;
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Queries.Internal.Parsing;
+
+namespace JsonApiDotNetCore.Queries.Expressions;
+
+/// <summary>
+/// Represents the "isType" filter function, resulting from text such as: isType(,men), isType(creator,men) or
+/// isType(creator,men,equals(hasBeard,'true'))
+/// </summary>
+[PublicAPI]
+public class IsTypeExpression : FilterExpression
+{
+    public ResourceFieldChainExpression? TargetToOneRelationship { get; }
+    public ResourceType DerivedType { get; }
+    public FilterExpression? Child { get; }
+
+    public IsTypeExpression(ResourceFieldChainExpression? targetToOneRelationship, ResourceType derivedType, FilterExpression? child)
+    {
+        ArgumentGuard.NotNull(derivedType, nameof(derivedType));
+
+        TargetToOneRelationship = targetToOneRelationship;
+        DerivedType = derivedType;
+        Child = child;
+    }
+
+    public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgument, TResult> visitor, TArgument argument)
+    {
+        return visitor.VisitIsType(this, argument);
+    }
+
+    public override string ToString()
+    {
+        var builder = new StringBuilder();
+        builder.Append(Keywords.IsType);
+        builder.Append('(');
+
+        if (TargetToOneRelationship != null)
+        {
+            builder.Append(TargetToOneRelationship);
+        }
+
+        builder.Append(',');
+        builder.Append(DerivedType);
+
+        if (Child != null)
+        {
+            builder.Append(',');
+            builder.Append(Child);
+        }
+
+        builder.Append(')');
+        return builder.ToString();
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (ReferenceEquals(this, obj))
+        {
+            return true;
+        }
+
+        if (obj is null || GetType() != obj.GetType())
+        {
+            return false;
+        }
+
+        var other = (IsTypeExpression)obj;
+
+        return Equals(TargetToOneRelationship, other.TargetToOneRelationship) && DerivedType.Equals(other.DerivedType) && Equals(Child, other.Child);
+    }
+
+    public override int GetHashCode()
+    {
+        return HashCode.Combine(TargetToOneRelationship, DerivedType, Child);
+    }
+}
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionRewriter.cs b/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionRewriter.cs
index cd5937cd80..7051e81f73 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionRewriter.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionRewriter.cs
@@ -91,6 +91,18 @@ public override QueryExpression VisitNullConstant(NullConstantExpression express
         return null;
     }
 
+    public override QueryExpression VisitIsType(IsTypeExpression expression, TArgument argument)
+    {
+        ResourceFieldChainExpression? newTargetToOneRelationship = expression.TargetToOneRelationship != null
+            ? Visit(expression.TargetToOneRelationship, argument) as ResourceFieldChainExpression
+            : null;
+
+        FilterExpression? newChild = expression.Child != null ? Visit(expression.Child, argument) as FilterExpression : null;
+
+        var newExpression = new IsTypeExpression(newTargetToOneRelationship, expression.DerivedType, newChild);
+        return newExpression.Equals(expression) ? expression : newExpression;
+    }
+
     public override QueryExpression? VisitSortElement(SortElementExpression expression, TArgument argument)
     {
         SortElementExpression? newExpression = null;
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionVisitor.cs b/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionVisitor.cs
index 7c893ba81c..7dcf44b1f4 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionVisitor.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/QueryExpressionVisitor.cs
@@ -53,6 +53,11 @@ public virtual TResult VisitHas(HasExpression expression, TArgument argument)
         return DefaultVisit(expression, argument);
     }
 
+    public virtual TResult VisitIsType(IsTypeExpression expression, TArgument argument)
+    {
+        return DefaultVisit(expression, argument);
+    }
+
     public virtual TResult VisitSortElement(SortElementExpression expression, TArgument argument)
     {
         return DefaultVisit(expression, argument);
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs
index c2b66f9063..5bd0a8d231 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs
@@ -28,15 +28,16 @@ public FilterExpression Parse(string source, ResourceType resourceTypeInScope)
     {
         ArgumentGuard.NotNull(resourceTypeInScope, nameof(resourceTypeInScope));
 
-        _resourceTypeInScope = resourceTypeInScope;
-
-        Tokenize(source);
+        return InScopeOfResourceType(resourceTypeInScope, () =>
+        {
+            Tokenize(source);
 
-        FilterExpression expression = ParseFilter();
+            FilterExpression expression = ParseFilter();
 
-        AssertTokenStackIsEmpty();
+            AssertTokenStackIsEmpty();
 
-        return expression;
+            return expression;
+        });
     }
 
     protected FilterExpression ParseFilter()
@@ -76,6 +77,10 @@ protected FilterExpression ParseFilter()
                 {
                     return ParseHas();
                 }
+                case Keywords.IsType:
+                {
+                    return ParseIsType();
+                }
             }
         }
 
@@ -259,13 +264,92 @@ protected HasExpression ParseHas()
 
     private FilterExpression ParseFilterInHas(HasManyAttribute hasManyRelationship)
     {
-        ResourceType outerScopeBackup = _resourceTypeInScope!;
+        return InScopeOfResourceType(hasManyRelationship.RightType, ParseFilter);
+    }
+
+    private IsTypeExpression ParseIsType()
+    {
+        EatText(Keywords.IsType);
+        EatSingleCharacterToken(TokenKind.OpenParen);
+
+        ResourceFieldChainExpression? targetToOneRelationship = TryParseToOneRelationshipChain();
+
+        EatSingleCharacterToken(TokenKind.Comma);
+
+        ResourceType baseType = targetToOneRelationship != null ? ((RelationshipAttribute)targetToOneRelationship.Fields[^1]).RightType : _resourceTypeInScope!;
+        ResourceType derivedType = ParseDerivedType(baseType);
+
+        FilterExpression? child = TryParseFilterInIsType(derivedType);
+
+        EatSingleCharacterToken(TokenKind.CloseParen);
+
+        return new IsTypeExpression(targetToOneRelationship, derivedType, child);
+    }
+
+    private ResourceFieldChainExpression? TryParseToOneRelationshipChain()
+    {
+        if (TokenStack.TryPeek(out Token? nextToken) && nextToken.Kind == TokenKind.Comma)
+        {
+            return null;
+        }
+
+        return ParseFieldChain(FieldChainRequirements.EndsInToOne, "Relationship name or , expected.");
+    }
+
+    private ResourceType ParseDerivedType(ResourceType baseType)
+    {
+        if (TokenStack.TryPop(out Token? token) && token.Kind == TokenKind.Text)
+        {
+            string derivedTypeName = token.Value!;
+            return ResolveDerivedType(baseType, derivedTypeName);
+        }
+
+        throw new QueryParseException("Resource type expected.");
+    }
+
+    private ResourceType ResolveDerivedType(ResourceType baseType, string derivedTypeName)
+    {
+        ResourceType? derivedType = GetDerivedType(baseType, derivedTypeName);
+
+        if (derivedType == null)
+        {
+            throw new QueryParseException($"Resource type '{derivedTypeName}' does not exist or does not derive from '{baseType.PublicName}'.");
+        }
+
+        return derivedType;
+    }
+
+    private ResourceType? GetDerivedType(ResourceType baseType, string publicName)
+    {
+        foreach (ResourceType derivedType in baseType.DirectlyDerivedTypes)
+        {
+            if (derivedType.PublicName == publicName)
+            {
+                return derivedType;
+            }
+
+            ResourceType? nextType = GetDerivedType(derivedType, publicName);
+
+            if (nextType != null)
+            {
+                return nextType;
+            }
+        }
+
+        return null;
+    }
+
+    private FilterExpression? TryParseFilterInIsType(ResourceType derivedType)
+    {
+        FilterExpression? filter = null;
 
-        _resourceTypeInScope = hasManyRelationship.RightType;
+        if (TokenStack.TryPeek(out Token? nextToken) && nextToken.Kind == TokenKind.Comma)
+        {
+            EatSingleCharacterToken(TokenKind.Comma);
 
-        FilterExpression filter = ParseFilter();
+            filter = InScopeOfResourceType(derivedType, ParseFilter);
+        }
 
-        _resourceTypeInScope = outerScopeBackup;
         return filter;
     }
 
@@ -349,6 +433,11 @@ protected override IImmutableList<ResourceFieldAttribute> OnResolveFieldChain(st
             return ChainResolver.ResolveToOneChainEndingInAttribute(_resourceTypeInScope!, path, _validateSingleFieldCallback);
         }
 
+        if (chainRequirements == FieldChainRequirements.EndsInToOne)
+        {
+            return ChainResolver.ResolveToOneChain(_resourceTypeInScope!, path, _validateSingleFieldCallback);
+        }
+
         if (chainRequirements.HasFlag(FieldChainRequirements.EndsInAttribute) && chainRequirements.HasFlag(FieldChainRequirements.EndsInToOne))
         {
             return ChainResolver.ResolveToOneChainEndingInAttributeOrToOne(_resourceTypeInScope!, path, _validateSingleFieldCallback);
@@ -356,4 +445,19 @@ protected override IImmutableList<ResourceFieldAttribute> OnResolveFieldChain(st
 
         throw new InvalidOperationException($"Unexpected combination of chain requirement flags '{chainRequirements}'.");
     }
+
+    private TResult InScopeOfResourceType<TResult>(ResourceType resourceType, Func<TResult> action)
+    {
+        ResourceType? backupType = _resourceTypeInScope;
+
+        try
+        {
+            _resourceTypeInScope = resourceType;
+            return action();
+        }
+        finally
+        {
+            _resourceTypeInScope = backupType;
+        }
+    }
 }
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/Keywords.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/Keywords.cs
index dd0bda51b7..790f8f544d 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/Keywords.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/Keywords.cs
@@ -23,4 +23,5 @@ public static class Keywords
     public const string Any = "any";
     public const string Count = "count";
     public const string Has = "has";
+    public const string IsType = "isType";
 }
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs
index 33f3643aa8..1b3ef7dcfe 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs
@@ -9,6 +9,32 @@ namespace JsonApiDotNetCore.Queries.Internal.Parsing;
 /// </summary>
 internal sealed class ResourceFieldChainResolver
 {
+    /// <summary>
+    /// Resolves a chain of to-one relationships.
+    /// <example>author</example>
+    /// <example>
+    /// author.address.country
+    /// </example>
+    /// </summary>
+    public IImmutableList<ResourceFieldAttribute> ResolveToOneChain(ResourceType resourceType, string path,
+        Action<ResourceFieldAttribute, ResourceType, string>? validateCallback = null)
+    {
+        ImmutableArray<ResourceFieldAttribute>.Builder chainBuilder = ImmutableArray.CreateBuilder<ResourceFieldAttribute>();
+        ResourceType nextResourceType = resourceType;
+
+        foreach (string publicName in path.Split("."))
+        {
+            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path);
+
+            validateCallback?.Invoke(toOneRelationship, nextResourceType, path);
+
+            chainBuilder.Add(toOneRelationship);
+            nextResourceType = toOneRelationship.RightType;
+        }
+
+        return chainBuilder.ToImmutable();
+    }
+
     /// <summary>
     /// Resolves a chain of relationships that ends in a to-many relationship, for example: blogs.owner.articles.comments
     /// </summary>
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScope.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScope.cs
index 8be9e4263e..e5502031a3 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScope.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScope.cs
@@ -14,15 +14,30 @@ public sealed class LambdaScope : IDisposable
     public ParameterExpression Parameter { get; }
     public Expression Accessor { get; }
 
-    public LambdaScope(LambdaParameterNameFactory nameFactory, Type elementType, Expression? accessorExpression)
+    private LambdaScope(LambdaParameterNameScope parameterNameScope, ParameterExpression parameter, Expression accessor)
+    {
+        _parameterNameScope = parameterNameScope;
+        Parameter = parameter;
+        Accessor = accessor;
+    }
+
+    public static LambdaScope Create(LambdaParameterNameFactory nameFactory, Type elementType, Expression? accessorExpression)
     {
         ArgumentGuard.NotNull(nameFactory, nameof(nameFactory));
         ArgumentGuard.NotNull(elementType, nameof(elementType));
 
-        _parameterNameScope = nameFactory.Create(elementType.Name);
-        Parameter = Expression.Parameter(elementType, _parameterNameScope.Name);
+        LambdaParameterNameScope parameterNameScope = nameFactory.Create(elementType.Name);
+        ParameterExpression parameter = Expression.Parameter(elementType, parameterNameScope.Name);
+        Expression accessor = accessorExpression ?? parameter;
+
+        return new LambdaScope(parameterNameScope, parameter, accessor);
+    }
+
+    public LambdaScope WithAccessor(Expression accessorExpression)
+    {
+        ArgumentGuard.NotNull(accessorExpression, nameof(accessorExpression));
 
-        Accessor = accessorExpression ?? Parameter;
+        return new LambdaScope(_parameterNameScope, Parameter, accessorExpression);
     }
 
     public void Dispose()
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScopeFactory.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScopeFactory.cs
index 3ba7c5aab9..9c13a63d28 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScopeFactory.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/LambdaScopeFactory.cs
@@ -19,6 +19,6 @@ public LambdaScope CreateScope(Type elementType, Expression? accessorExpression
     {
         ArgumentGuard.NotNull(elementType, nameof(elementType));
 
-        return new LambdaScope(_nameFactory, elementType, accessorExpression);
+        return LambdaScope.Create(_nameFactory, elementType, accessorExpression);
     }
 }
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs
index bf14c70b6d..de80d8a6ff 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs
@@ -9,7 +9,7 @@ namespace JsonApiDotNetCore.Queries.Internal.QueryableBuilding;
 /// </summary>
 public abstract class QueryClauseBuilder<TArgument> : QueryExpressionVisitor<TArgument, Expression>
 {
-    protected LambdaScope LambdaScope { get; }
+    protected LambdaScope LambdaScope { get; private set; }
 
     protected QueryClauseBuilder(LambdaScope lambdaScope)
     {
@@ -83,4 +83,24 @@ private static MemberExpression CreatePropertyExpressionFromComponents(Expressio
 
         return property!;
     }
+
+    protected TResult WithLambdaScopeAccessor<TResult>(Expression accessorExpression, Func<TResult> action)
+    {
+        ArgumentGuard.NotNull(accessorExpression, nameof(accessorExpression));
+        ArgumentGuard.NotNull(action, nameof(action));
+
+        LambdaScope backupScope = LambdaScope;
+
+        try
+        {
+            using (LambdaScope = LambdaScope.WithAccessor(accessorExpression))
+            {
+                return action();
+            }
+        }
+        finally
+        {
+            LambdaScope = backupScope;
+        }
+    }
 }
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs
index e643cc5b3a..fbf3f8ebca 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs
@@ -194,7 +194,8 @@ private static void IncludeEagerLoads(ResourceType resourceType, Dictionary<Prop
 
     private MemberAssignment CreatePropertyAssignment(PropertySelector propertySelector, LambdaScope lambdaScope)
     {
-        bool requiresUpCast = !propertySelector.Property.DeclaringType!.IsAssignableFrom(lambdaScope.Accessor.Type);
+        bool requiresUpCast = lambdaScope.Accessor.Type != propertySelector.Property.DeclaringType &&
+            lambdaScope.Accessor.Type.IsAssignableFrom(propertySelector.Property.DeclaringType);
 
         MemberExpression propertyAccess = requiresUpCast
             ? Expression.MakeMemberAccess(Expression.Convert(lambdaScope.Accessor, propertySelector.Property.DeclaringType!), propertySelector.Property)
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/WhereClauseBuilder.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/WhereClauseBuilder.cs
index e34da3a495..2806e96da4 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/WhereClauseBuilder.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/WhereClauseBuilder.cs
@@ -85,6 +85,22 @@ private static MethodCallExpression AnyExtensionMethodCall(Type elementType, Exp
             : Expression.Call(typeof(Enumerable), "Any", elementType.AsArray(), source);
     }
 
+    public override Expression VisitIsType(IsTypeExpression expression, Type? argument)
+    {
+        Expression property = expression.TargetToOneRelationship != null ? Visit(expression.TargetToOneRelationship, argument) : LambdaScope.Accessor;
+        TypeBinaryExpression typeCheck = Expression.TypeIs(property, expression.DerivedType.ClrType);
+
+        if (expression.Child == null)
+        {
+            return typeCheck;
+        }
+
+        UnaryExpression derivedAccessor = Expression.Convert(property, expression.DerivedType.ClrType);
+        Expression filter = WithLambdaScopeAccessor(derivedAccessor, () => Visit(expression.Child, argument));
+
+        return Expression.AndAlso(typeCheck, filter);
+    }
+
     public override Expression VisitMatchText(MatchTextExpression expression, Type? argument)
     {
         Expression property = Visit(expression.TargetAttribute, argument);
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
index f9c2bb0ac7..ed6897c7c2 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
@@ -1623,4 +1623,205 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
   ]
 }}");
     }
+
+    [Fact]
+    public async Task Can_filter_on_derived_resource_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Tandem tandem = _fakers.Tandem.Generate();
+
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem, car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/vehicles?filter=isType(,bikes)";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(2);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "bikes" && resource.Id == bike.StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems" && resource.Id == tandem.StringId);
+    }
+
+    [Fact]
+    public async Task Can_filter_on_derived_resource_type_with_condition_at_abstract_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Car car = _fakers.Car.Generate();
+        car.LicensePlate = "XX-99-YY";
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        Truck truck = _fakers.Truck.Generate();
+        truck.LicensePlate = "AA-11-BB";
+        truck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, car, truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/vehicles?filter=isType(,motorVehicles,equals(licensePlate,'AA-11-BB'))";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(1);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "trucks" && resource.Id == truck.StringId);
+    }
+
+    [Fact]
+    public async Task Can_filter_on_derived_resource_type_and_derived_ToOne_relationship_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, car, truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/vehicles?filter=isType(,motorVehicles,isType(engine,dieselEngines))";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(1);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "trucks" && resource.Id == truck.StringId);
+    }
+
+    [Fact]
+    public async Task Can_filter_on_derived_resource_type_and_derived_ToOne_relationship_type_with_condition_at_abstract_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        Truck truck1 = _fakers.Truck.Generate();
+        truck1.Engine = _fakers.DieselEngine.Generate();
+        ((DieselEngine)truck1.Engine).Viscosity = 25;
+
+        Truck truck2 = _fakers.Truck.Generate();
+        truck2.Engine = _fakers.DieselEngine.Generate();
+        ((DieselEngine)truck2.Engine).Viscosity = 100;
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(car, truck1, truck2);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/vehicles?filter=isType(,motorVehicles,isType(engine,dieselEngines,greaterThan(viscosity,'50')))";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(1);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "trucks" && resource.Id == truck2.StringId);
+    }
+
+    [Fact]
+    public async Task Can_filter_on_derived_resource_type_with_condition_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Tandem tandem1 = _fakers.Tandem.Generate();
+
+        Tandem tandem2 = _fakers.Tandem.Generate();
+        tandem2.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem1, tandem2);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/bikes?filter=isType(,tandems,has(features))";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(1);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "tandems" && resource.Id == tandem2.StringId);
+    }
+
+    [Fact]
+    public async Task Can_filter_on_derived_resource_type_with_condition_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Car car1 = _fakers.Car.Generate();
+        car1.Engine = _fakers.GasolineEngine.Generate();
+        car1.Wheels = _fakers.CarbonWheel.Generate(4).Cast<Wheel>().ToHashSet();
+
+        Car car2 = _fakers.Car.Generate();
+        car2.Engine = _fakers.GasolineEngine.Generate();
+        car2.Wheels = _fakers.ChromeWheel.Generate(4).Cast<Wheel>().ToHashSet();
+
+        Car car3 = _fakers.Car.Generate();
+        car3.Engine = _fakers.GasolineEngine.Generate();
+        car3.Wheels = _fakers.ChromeWheel.Generate(4).Cast<Wheel>().ToHashSet();
+        car3.Wheels.Cast<ChromeWheel>().ElementAt(0).PaintColor = "light-gray";
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(car1, car2, car3);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/cars?filter=has(wheels,isType(,chromeWheels,equals(paintColor,'light-gray')))";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(1);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "cars" && resource.Id == car3.StringId);
+    }
 }
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/FilterParseTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/FilterParseTests.cs
index 17ee7dba92..e471218ff6 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/FilterParseTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/FilterParseTests.cs
@@ -95,6 +95,15 @@ public void Reader_Is_Enabled(JsonApiQueryStringParameters parametersDisabled, b
     [InlineData("filter", "and(null", "Filter function expected.")]
     [InlineData("filter", "expr:equals(caption,'some')", "Filter function expected.")]
     [InlineData("filter", "expr:Equals(caption,'some')", "Filter function expected.")]
+    [InlineData("filter", "isType(", "Relationship name or , expected.")]
+    [InlineData("filter", "isType(,", "Resource type expected.")]
+    [InlineData("filter[posts.contributors]", "isType(,some)", "Resource type 'some' does not exist or does not derive from 'humans'.")]
+    [InlineData("filter[posts.contributors]", "isType(,humans)", "Resource type 'humans' does not exist or does not derive from 'humans'.")]
+    [InlineData("filter[posts.contributors]", "isType(some,men)", "Relationship 'some' does not exist on resource type 'humans'.")]
+    [InlineData("filter[posts.contributors]", "isType(father.some,women)", "Relationship 'some' in 'father.some' does not exist on resource type 'men'.")]
+    [InlineData("filter[posts.contributors]", "isType(children,men)", "Relationship 'children' must be a to-one relationship on resource type 'humans'.")]
+    [InlineData("filter[posts.contributors]", "isType(mother.children,men)",
+        "Relationship 'children' in 'mother.children' must be a to-one relationship on resource type 'women'.")]
     public void Reader_Read_Fails(string parameterName, string parameterValue, string errorMessage)
     {
         // Act
@@ -142,6 +151,10 @@ public void Reader_Read_Fails(string parameterName, string parameterValue, strin
         "and(contains(title,'sales'),contains(title,'marketing'),contains(title,'advertising'))")]
     [InlineData("filter[posts]", "or(and(not(equals(author.userName,null)),not(equals(author.displayName,null))),not(has(comments,startsWith(text,'A'))))",
         "posts", "or(and(not(equals(author.userName,null)),not(equals(author.displayName,null))),not(has(comments,startsWith(text,'A'))))")]
+    [InlineData("filter", "isType(owner.person,men)", null, "isType(owner.person,men)")]
+    [InlineData("filter", "isType(owner.person,men,equals(hasBeard,'true'))", null, "isType(owner.person,men,equals(hasBeard,'true'))")]
+    [InlineData("filter[posts.contributors]", "isType(,women)", "posts.contributors", "isType(,women)")]
+    [InlineData("filter[posts.contributors]", "isType(,women,equals(maidenName,'Austen'))", "posts.contributors", "isType(,women,equals(maidenName,'Austen'))")]
     public void Reader_Read_Succeeds(string parameterName, string parameterValue, string scopeExpected, string valueExpected)
     {
         // Act

From c1ac4578ad2beab425ae6de17af514e902baba61 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Sun, 20 Mar 2022 01:14:06 +0100
Subject: [PATCH 07/19] Added ResourceFieldAttribute.Type and use it from
 QueryExpression.ToFullString() to provide improved debug info

---
 .../Annotations/RelationshipAttribute.cs      | 41 +++++++++---------
 .../Annotations/ResourceFieldAttribute.cs     | 15 +++++++
 .../Configuration/ResourceGraphBuilder.cs     | 30 ++++++-------
 .../Queries/Expressions/AnyExpression.cs      | 14 ++++++-
 .../Expressions/ComparisonExpression.cs       |  5 +++
 .../Queries/Expressions/CountExpression.cs    |  5 +++
 .../Queries/Expressions/HasExpression.cs      | 14 ++++++-
 .../Expressions/IncludeElementExpression.cs   | 14 ++++++-
 .../Queries/Expressions/IncludeExpression.cs  | 12 +++++-
 .../Queries/Expressions/IsTypeExpression.cs   | 14 ++++++-
 .../Expressions/LiteralConstantExpression.cs  |  5 +++
 .../Queries/Expressions/LogicalExpression.cs  | 12 +++++-
 .../Expressions/MatchTextExpression.cs        | 16 ++++++-
 .../Queries/Expressions/NotExpression.cs      |  5 +++
 .../Expressions/NullConstantExpression.cs     |  5 +++
 ...nationElementQueryStringValueExpression.cs |  5 +++
 .../Expressions/PaginationExpression.cs       |  5 +++
 .../PaginationQueryStringValueExpression.cs   |  7 +++-
 .../Queries/Expressions/QueryExpression.cs    |  2 +
 .../QueryStringParameterScopeExpression.cs    |  5 +++
 .../Expressions/QueryableHandlerExpression.cs |  5 +++
 .../ResourceFieldChainExpression.cs           |  5 +++
 .../Expressions/SortElementExpression.cs      | 14 ++++++-
 .../Queries/Expressions/SortExpression.cs     |  5 +++
 .../Expressions/SparseFieldSetExpression.cs   |  7 +++-
 .../Expressions/SparseFieldTableExpression.cs | 14 ++++++-
 .../Queries/Internal/Parsing/IncludeParser.cs | 42 +------------------
 .../UnitTests/Links/LinkInclusionTests.cs     |  4 +-
 28 files changed, 232 insertions(+), 95 deletions(-)

diff --git a/src/JsonApiDotNetCore.Annotations/Resources/Annotations/RelationshipAttribute.cs b/src/JsonApiDotNetCore.Annotations/Resources/Annotations/RelationshipAttribute.cs
index 6406ba17ff..11320a7abc 100644
--- a/src/JsonApiDotNetCore.Annotations/Resources/Annotations/RelationshipAttribute.cs
+++ b/src/JsonApiDotNetCore.Annotations/Resources/Annotations/RelationshipAttribute.cs
@@ -14,21 +14,8 @@ public abstract class RelationshipAttribute : ResourceFieldAttribute
 {
     private protected static readonly CollectionConverter CollectionConverter = new();
 
-    /// <summary>
-    /// The CLR type in which this relationship is declared.
-    /// </summary>
-    internal Type? LeftClrType { get; set; }
-
-    /// <summary>
-    /// The CLR type this relationship points to. In the case of a <see cref="HasManyAttribute" /> relationship, this value will be the collection element
-    /// type.
-    /// </summary>
-    /// <example>
-    /// <code><![CDATA[
-    /// public ISet<Tag> Tags { get; set; } // RightClrType: typeof(Tag)
-    /// ]]></code>
-    /// </example>
-    internal Type? RightClrType { get; set; }
+    // These are definitely assigned after building the resource graph, which is why their public equivalents are declared as non-nullable.
+    private ResourceType? _rightType;
 
     /// <summary>
     /// The <see cref="PropertyInfo" /> of the Entity Framework Core inverse navigation, which may or may not exist. Even if it exists, it may not be exposed
@@ -52,15 +39,28 @@ public abstract class RelationshipAttribute : ResourceFieldAttribute
     public PropertyInfo? InverseNavigationProperty { get; set; }
 
     /// <summary>
-    /// The containing resource type in which this relationship is declared.
+    /// The containing resource type in which this relationship is declared. Identical to <see cref="ResourceFieldAttribute.Type" />.
     /// </summary>
-    public ResourceType LeftType { get; internal set; } = null!;
+    public ResourceType LeftType => Type;
 
     /// <summary>
     /// The resource type this relationship points to. In the case of a <see cref="HasManyAttribute" /> relationship, this value will be the collection
     /// element type.
     /// </summary>
-    public ResourceType RightType { get; internal set; } = null!;
+    /// <example>
+    /// <code><![CDATA[
+    /// public ISet<Tag> Tags { get; set; } // RightType: Tag
+    /// ]]></code>
+    /// </example>
+    public ResourceType RightType
+    {
+        get => _rightType!;
+        internal set
+        {
+            ArgumentGuard.NotNull(value, nameof(value));
+            _rightType = value;
+        }
+    }
 
     /// <summary>
     /// Configures which links to write in the relationship-level links object for this relationship. Defaults to <see cref="LinkTypes.NotConfigured" />,
@@ -91,12 +91,11 @@ public override bool Equals(object? obj)
 
         var other = (RelationshipAttribute)obj;
 
-        return LeftClrType == other.LeftClrType && RightClrType == other.RightClrType && Links == other.Links && CanInclude == other.CanInclude &&
-            base.Equals(other);
+        return _rightType?.ClrType == other._rightType?.ClrType && Links == other.Links && CanInclude == other.CanInclude && base.Equals(other);
     }
 
     public override int GetHashCode()
     {
-        return HashCode.Combine(LeftClrType, RightClrType, Links, CanInclude, base.GetHashCode());
+        return HashCode.Combine(_rightType?.ClrType, Links, CanInclude, base.GetHashCode());
     }
 }
diff --git a/src/JsonApiDotNetCore.Annotations/Resources/Annotations/ResourceFieldAttribute.cs b/src/JsonApiDotNetCore.Annotations/Resources/Annotations/ResourceFieldAttribute.cs
index c7a44f59c8..599b17a42a 100644
--- a/src/JsonApiDotNetCore.Annotations/Resources/Annotations/ResourceFieldAttribute.cs
+++ b/src/JsonApiDotNetCore.Annotations/Resources/Annotations/ResourceFieldAttribute.cs
@@ -1,5 +1,6 @@
 using System.Reflection;
 using JetBrains.Annotations;
+using JsonApiDotNetCore.Configuration;
 
 // ReSharper disable NonReadonlyMemberInGetHashCode
 
@@ -15,6 +16,7 @@ public abstract class ResourceFieldAttribute : Attribute
     // These are definitely assigned after building the resource graph, which is why their public equivalents are declared as non-nullable.
     private string? _publicName;
     private PropertyInfo? _property;
+    private ResourceType? _type;
 
     /// <summary>
     /// The publicly exposed name of this JSON:API field. When not explicitly assigned, the configured naming convention is applied on the property name.
@@ -46,6 +48,19 @@ internal set
         }
     }
 
+    /// <summary>
+    /// The containing resource type in which this field is declared.
+    /// </summary>
+    public ResourceType Type
+    {
+        get => _type!;
+        internal set
+        {
+            ArgumentGuard.NotNull(value, nameof(value));
+            _type = value;
+        }
+    }
+
     /// <summary>
     /// Gets the value of this field on the specified resource instance. Throws if the property is write-only or if the field does not belong to the
     /// specified resource instance.
diff --git a/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs b/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
index f4ac78049d..397226ff43 100644
--- a/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
+++ b/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
@@ -43,23 +43,35 @@ public IResourceGraph Build()
 
         var resourceGraph = new ResourceGraph(resourceTypes);
 
+        SetFieldTypes(resourceGraph);
         SetRelationshipTypes(resourceGraph);
         SetDirectlyDerivedTypes(resourceGraph);
 
         return resourceGraph;
     }
 
+    private static void SetFieldTypes(ResourceGraph resourceGraph)
+    {
+        foreach (ResourceFieldAttribute field in resourceGraph.GetResourceTypes().SelectMany(resourceType => resourceType.Fields))
+        {
+            field.Type = resourceGraph.GetResourceType(field.Property.ReflectedType!);
+        }
+    }
+
     private static void SetRelationshipTypes(ResourceGraph resourceGraph)
     {
         foreach (RelationshipAttribute relationship in resourceGraph.GetResourceTypes().SelectMany(resourceType => resourceType.Relationships))
         {
-            relationship.LeftType = resourceGraph.GetResourceType(relationship.LeftClrType!);
-            ResourceType? rightType = resourceGraph.FindResourceType(relationship.RightClrType!);
+            Type rightClrType = relationship is HasOneAttribute
+                ? relationship.Property.PropertyType
+                : relationship.Property.PropertyType.GetGenericArguments()[0];
+
+            ResourceType? rightType = resourceGraph.FindResourceType(rightClrType);
 
             if (rightType == null)
             {
-                throw new InvalidConfigurationException($"Resource type '{relationship.LeftClrType}' depends on " +
-                    $"'{relationship.RightClrType}', which was not added to the resource graph.");
+                throw new InvalidConfigurationException($"Resource type '{relationship.LeftType.ClrType}' depends on " +
+                    $"'{rightClrType}', which was not added to the resource graph.");
             }
 
             relationship.RightType = rightType;
@@ -254,8 +266,6 @@ private IReadOnlyCollection<RelationshipAttribute> GetRelationships(Type resourc
             {
                 relationship.Property = property;
                 SetPublicName(relationship, property);
-                relationship.LeftClrType = resourceClrType;
-                relationship.RightClrType = GetRelationshipType(relationship, property);
 
                 IncludeField(relationshipsByName, relationship);
             }
@@ -270,14 +280,6 @@ private void SetPublicName(ResourceFieldAttribute field, PropertyInfo property)
         field.PublicName ??= FormatPropertyName(property);
     }
 
-    private Type GetRelationshipType(RelationshipAttribute relationship, PropertyInfo property)
-    {
-        ArgumentGuard.NotNull(relationship, nameof(relationship));
-        ArgumentGuard.NotNull(property, nameof(property));
-
-        return relationship is HasOneAttribute ? property.PropertyType : property.PropertyType.GetGenericArguments()[0];
-    }
-
     private IReadOnlyCollection<EagerLoadAttribute> GetEagerLoads(Type resourceClrType, int recursionDepth = 0)
     {
         AssertNoInfiniteRecursion(recursionDepth);
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/AnyExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/AnyExpression.cs
index be8a22abee..980a7846bc 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/AnyExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/AnyExpression.cs
@@ -34,14 +34,24 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
 
         builder.Append(Keywords.Any);
         builder.Append('(');
-        builder.Append(TargetAttribute);
+        builder.Append(toFullString ? TargetAttribute.ToFullString() : TargetAttribute);
         builder.Append(',');
-        builder.Append(string.Join(",", Constants.Select(constant => constant.ToString()).OrderBy(value => value)));
+        builder.Append(string.Join(",", Constants.Select(constant => toFullString ? constant.ToFullString() : constant.ToString()).OrderBy(value => value)));
         builder.Append(')');
 
         return builder.ToString();
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/ComparisonExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/ComparisonExpression.cs
index 4c858bd743..9bf1c3bde8 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/ComparisonExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/ComparisonExpression.cs
@@ -33,6 +33,11 @@ public override string ToString()
         return $"{Operator.ToString().Camelize()}({Left},{Right})";
     }
 
+    public override string ToFullString()
+    {
+        return $"{Operator.ToString().Camelize()}({Left.ToFullString()},{Right.ToFullString()})";
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/CountExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/CountExpression.cs
index 1bab96eaab..5de89ead7c 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/CountExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/CountExpression.cs
@@ -28,6 +28,11 @@ public override string ToString()
         return $"{Keywords.Count}({TargetCollection})";
     }
 
+    public override string ToFullString()
+    {
+        return $"{Keywords.Count}({TargetCollection.ToFullString()})";
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/HasExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/HasExpression.cs
index d1376a3091..c5387106d6 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/HasExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/HasExpression.cs
@@ -27,16 +27,26 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
         builder.Append(Keywords.Has);
         builder.Append('(');
-        builder.Append(TargetCollection);
+        builder.Append(toFullString ? TargetCollection.ToFullString() : TargetCollection);
 
         if (Filter != null)
         {
             builder.Append(',');
-            builder.Append(Filter);
+            builder.Append(toFullString ? Filter.ToFullString() : Filter);
         }
 
         builder.Append(')');
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/IncludeElementExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/IncludeElementExpression.cs
index cd95ef61a3..e76aaf0946 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/IncludeElementExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/IncludeElementExpression.cs
@@ -34,14 +34,24 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
-        builder.Append(Relationship);
+        builder.Append(toFullString ? $"{Relationship.LeftType.PublicName}:{Relationship.PublicName}" : Relationship.PublicName);
 
         if (Children.Any())
         {
             builder.Append('{');
-            builder.Append(string.Join(",", Children.Select(child => child.ToString()).OrderBy(name => name)));
+            builder.Append(string.Join(",", Children.Select(child => toFullString ? child.ToFullString() : child.ToString()).OrderBy(name => name)));
             builder.Append('}');
         }
 
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/IncludeExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/IncludeExpression.cs
index 4597570ba3..a63d87719d 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/IncludeExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/IncludeExpression.cs
@@ -33,9 +33,19 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         IReadOnlyCollection<ResourceFieldChainExpression> chains = IncludeChainConverter.GetRelationshipChains(this);
-        return string.Join(",", chains.Select(child => child.ToString()).OrderBy(name => name));
+        return string.Join(",", chains.Select(field => toFullString ? field.ToFullString() : field.ToString()).OrderBy(name => name));
     }
 
     public override bool Equals(object? obj)
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs
index 5277b2b71b..a30e31308b 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/IsTypeExpression.cs
@@ -31,6 +31,16 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
         builder.Append(Keywords.IsType);
@@ -38,7 +48,7 @@ public override string ToString()
 
         if (TargetToOneRelationship != null)
         {
-            builder.Append(TargetToOneRelationship);
+            builder.Append(toFullString ? TargetToOneRelationship.ToFullString() : TargetToOneRelationship);
         }
 
         builder.Append(',');
@@ -47,7 +57,7 @@ public override string ToString()
         if (Child != null)
         {
             builder.Append(',');
-            builder.Append(Child);
+            builder.Append(toFullString ? Child.ToFullString() : Child);
         }
 
         builder.Append(')');
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/LiteralConstantExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/LiteralConstantExpression.cs
index bc5b4790ac..17c62f230f 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/LiteralConstantExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/LiteralConstantExpression.cs
@@ -28,6 +28,11 @@ public override string ToString()
         return $"'{value}'";
     }
 
+    public override string ToFullString()
+    {
+        return ToString();
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/LogicalExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/LogicalExpression.cs
index 0308c04de2..c8d8ffb24b 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/LogicalExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/LogicalExpression.cs
@@ -47,12 +47,22 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
 
         builder.Append(Operator.ToString().Camelize());
         builder.Append('(');
-        builder.Append(string.Join(",", Terms.Select(term => term.ToString())));
+        builder.Append(string.Join(",", Terms.Select(term => toFullString ? term.ToFullString() : term.ToString())));
         builder.Append(')');
 
         return builder.ToString();
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/MatchTextExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/MatchTextExpression.cs
index f528790fd3..a9c598402b 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/MatchTextExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/MatchTextExpression.cs
@@ -30,12 +30,26 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
 
         builder.Append(MatchKind.ToString().Camelize());
         builder.Append('(');
-        builder.Append(string.Join(",", TargetAttribute, TextValue));
+
+        builder.Append(toFullString
+            ? string.Join(",", TargetAttribute.ToFullString(), TextValue.ToFullString())
+            : string.Join(",", TargetAttribute, TextValue));
+
         builder.Append(')');
 
         return builder.ToString();
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/NotExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/NotExpression.cs
index c6d13f9876..4d28c4a9c3 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/NotExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/NotExpression.cs
@@ -28,6 +28,11 @@ public override string ToString()
         return $"{Keywords.Not}({Child})";
     }
 
+    public override string ToFullString()
+    {
+        return $"{Keywords.Not}({Child.ToFullString()})";
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/NullConstantExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/NullConstantExpression.cs
index bd9d3cf268..bdf1af317d 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/NullConstantExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/NullConstantExpression.cs
@@ -25,6 +25,11 @@ public override string ToString()
         return Keywords.Null;
     }
 
+    public override string ToFullString()
+    {
+        return ToString();
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/PaginationElementQueryStringValueExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/PaginationElementQueryStringValueExpression.cs
index d60282bcb0..88846f3708 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/PaginationElementQueryStringValueExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/PaginationElementQueryStringValueExpression.cs
@@ -27,6 +27,11 @@ public override string ToString()
         return Scope == null ? Value.ToString() : $"{Scope}: {Value}";
     }
 
+    public override string ToFullString()
+    {
+        return Scope == null ? Value.ToString() : $"{Scope.ToFullString()}: {Value}";
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/PaginationExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/PaginationExpression.cs
index 4b88ca55da..97ff8b1456 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/PaginationExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/PaginationExpression.cs
@@ -30,6 +30,11 @@ public override string ToString()
         return PageSize != null ? $"Page number: {PageNumber}, size: {PageSize}" : "(none)";
     }
 
+    public override string ToFullString()
+    {
+        return ToString();
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/PaginationQueryStringValueExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/PaginationQueryStringValueExpression.cs
index 68eb353b5c..594dab297a 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/PaginationQueryStringValueExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/PaginationQueryStringValueExpression.cs
@@ -25,7 +25,12 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
 
     public override string ToString()
     {
-        return string.Join(",", Elements.Select(constant => constant.ToString()));
+        return string.Join(",", Elements.Select(element => element.ToString()));
+    }
+
+    public override string ToFullString()
+    {
+        return string.Join(",", Elements.Select(element => element.ToFullString()));
     }
 
     public override bool Equals(object? obj)
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/QueryExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/QueryExpression.cs
index e442e6968d..2ff93dafe4 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/QueryExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/QueryExpression.cs
@@ -9,4 +9,6 @@ namespace JsonApiDotNetCore.Queries.Expressions;
 public abstract class QueryExpression
 {
     public abstract TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgument, TResult> visitor, TArgument argument);
+
+    public abstract string ToFullString();
 }
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/QueryStringParameterScopeExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/QueryStringParameterScopeExpression.cs
index db0e887c09..e567da8778 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/QueryStringParameterScopeExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/QueryStringParameterScopeExpression.cs
@@ -29,6 +29,11 @@ public override string ToString()
         return Scope == null ? ParameterName.ToString() : $"{ParameterName}: {Scope}";
     }
 
+    public override string ToFullString()
+    {
+        return Scope == null ? ParameterName.ToFullString() : $"{ParameterName.ToFullString()}: {Scope.ToFullString()}";
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/QueryableHandlerExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/QueryableHandlerExpression.cs
index bffd8ae0ce..1d9c910955 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/QueryableHandlerExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/QueryableHandlerExpression.cs
@@ -38,6 +38,11 @@ public override string ToString()
         return $"handler('{_parameterValue}')";
     }
 
+    public override string ToFullString()
+    {
+        return ToString();
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/ResourceFieldChainExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/ResourceFieldChainExpression.cs
index 7f19c55ba0..7decec6221 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/ResourceFieldChainExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/ResourceFieldChainExpression.cs
@@ -36,6 +36,11 @@ public override string ToString()
         return string.Join(".", Fields.Select(field => field.PublicName));
     }
 
+    public override string ToFullString()
+    {
+        return string.Join(".", Fields.Select(field => $"{field.Type.PublicName}:{field.PublicName}"));
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/SortElementExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/SortElementExpression.cs
index 9de73655ad..78de440a42 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/SortElementExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/SortElementExpression.cs
@@ -35,6 +35,16 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
 
@@ -45,11 +55,11 @@ public override string ToString()
 
         if (TargetAttribute != null)
         {
-            builder.Append(TargetAttribute);
+            builder.Append(toFullString ? TargetAttribute.ToFullString() : TargetAttribute);
         }
         else if (Count != null)
         {
-            builder.Append(Count);
+            builder.Append(toFullString ? Count.ToFullString() : Count);
         }
 
         return builder.ToString();
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/SortExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/SortExpression.cs
index b61b34eb91..dc0aebd320 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/SortExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/SortExpression.cs
@@ -28,6 +28,11 @@ public override string ToString()
         return string.Join(",", Elements.Select(child => child.ToString()));
     }
 
+    public override string ToFullString()
+    {
+        return string.Join(",", Elements.Select(child => child.ToFullString()));
+    }
+
     public override bool Equals(object? obj)
     {
         if (ReferenceEquals(this, obj))
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpression.cs
index c0532070e5..bc1e611bd8 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpression.cs
@@ -26,7 +26,12 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
 
     public override string ToString()
     {
-        return string.Join(",", Fields.Select(child => child.PublicName).OrderBy(name => name));
+        return string.Join(",", Fields.Select(field => field.PublicName).OrderBy(name => name));
+    }
+
+    public override string ToFullString()
+    {
+        return string.Join(".", Fields.Select(field => $"{field.Type.PublicName}:{field.PublicName}").OrderBy(name => name));
     }
 
     public override bool Equals(object? obj)
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldTableExpression.cs b/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldTableExpression.cs
index 8ec77f12fc..8e52df9b3b 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldTableExpression.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldTableExpression.cs
@@ -26,10 +26,20 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
     }
 
     public override string ToString()
+    {
+        return InnerToString(false);
+    }
+
+    public override string ToFullString()
+    {
+        return InnerToString(true);
+    }
+
+    private string InnerToString(bool toFullString)
     {
         var builder = new StringBuilder();
 
-        foreach ((ResourceType resourceType, SparseFieldSetExpression fields) in Table)
+        foreach ((ResourceType resourceType, SparseFieldSetExpression fieldSet) in Table)
         {
             if (builder.Length > 0)
             {
@@ -38,7 +48,7 @@ public override string ToString()
 
             builder.Append(resourceType.PublicName);
             builder.Append('(');
-            builder.Append(fields);
+            builder.Append(toFullString ? fieldSet.ToFullString() : fieldSet);
             builder.Append(')');
         }
 
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
index 15e9f4bd03..a64f0b0b68 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
@@ -296,47 +296,7 @@ private IncludeElementExpression ToElementExpression()
         public override string ToString()
         {
             IncludeExpression include = ToExpression();
-
-            IncludeChainConverter includeChainConverter = new();
-            IReadOnlyCollection<ResourceFieldChainExpression> chains = includeChainConverter.GetRelationshipChains(include);
-
-            IEnumerable<ResourceFieldChainExpression> chainsInOrder = InDisplayOrder(chains);
-            return string.Join(",", chainsInOrder.Select(RelationshipChainToString));
-        }
-
-        private static IEnumerable<ResourceFieldChainExpression> InDisplayOrder(IEnumerable<ResourceFieldChainExpression> chains)
-        {
-            return chains.OrderBy(chain => string.Join('.',
-                chain.Fields.OfType<RelationshipAttribute>().Select(relationship => relationship.PublicName + "@" + relationship.LeftType.PublicName)));
-        }
-
-        private static string RelationshipChainToString(ResourceFieldChainExpression chain)
-        {
-            var textBuilder = new StringBuilder();
-
-            ResourceType? parentType = null;
-
-            foreach (RelationshipAttribute relationship in chain.Fields.Cast<RelationshipAttribute>())
-            {
-                if (textBuilder.Length > 0)
-                {
-                    textBuilder.Append('.');
-                }
-
-                if (parentType == null || !parentType.Equals(relationship.LeftType))
-                {
-                    // This is not official syntax at this time, just helpful for debugging the parser.
-                    textBuilder.Append('[');
-                    textBuilder.Append(relationship.LeftType.PublicName);
-                    textBuilder.Append(']');
-                }
-
-                textBuilder.Append(relationship.PublicName);
-
-                parentType = relationship.RightType;
-            }
-
-            return textBuilder.ToString();
+            return include.ToFullString();
         }
 
         private sealed class HiddenRootRelationship : RelationshipAttribute
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Links/LinkInclusionTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/Links/LinkInclusionTests.cs
index 81bd4a6ef6..774d34a806 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/Links/LinkInclusionTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Links/LinkInclusionTests.cs
@@ -71,7 +71,7 @@ public void Applies_cascading_settings_for_top_level_links(LinkTypes linksInReso
             Kind = EndpointKind.Relationship,
             Relationship = new HasOneAttribute
             {
-                LeftType = exampleResourceType
+                Type = exampleResourceType
             }
         };
 
@@ -330,7 +330,7 @@ public void Applies_cascading_settings_for_relationship_links(LinkTypes linksInR
         var relationship = new HasOneAttribute
         {
             Links = linksInRelationshipAttribute,
-            LeftType = exampleResourceType
+            Type = exampleResourceType
         };
 
         // Act

From 1b2c75ecec4686722c52f38d0973208b8c87a268 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Sat, 19 Mar 2022 11:32:47 +0100
Subject: [PATCH 08/19] Resource inheritance: sorting on derived fields

---
 .../Configuration/ResourceType.cs             |  55 +++
 .../Configuration/IResourceGraph.cs           |   6 +-
 .../Configuration/ResourceGraph.cs            |  10 +-
 .../SparseFieldSetExpressionExtensions.cs     |   4 +-
 .../FieldChainInheritanceRequirement.cs       |  17 +
 .../Queries/Internal/Parsing/FilterParser.cs  |   6 +-
 .../Queries/Internal/Parsing/IncludeParser.cs |  51 +--
 .../Internal/Parsing/ResourceFieldCategory.cs |   8 +
 .../ResourceFieldChainErrorFormatter.cs       |  83 ++++
 .../Parsing/ResourceFieldChainResolver.cs     | 101 +++--
 .../Queries/Internal/Parsing/SortParser.cs    |  30 +-
 .../QueryableBuilding/QueryClauseBuilder.cs   |  21 +-
 .../Resources/JsonApiResourceDefinition.cs    |  34 +-
 .../SortExpressionLambdaConverter.cs          | 167 +++++++
 .../IntegrationTests/QueryStrings/Man.cs      |   6 +
 .../IntegrationTests/QueryStrings/Woman.cs    |   3 +
 .../ResourceInheritanceTests.cs               | 293 ++++++++++++
 .../WheelSortDefinition.cs                    |  69 +++
 .../QueryStringParameters/SortParseTests.cs   |  11 +
 .../CreateSortExpressionFromLambdaTests.cs    | 428 ++++++++++++++++++
 20 files changed, 1285 insertions(+), 118 deletions(-)
 create mode 100644 src/JsonApiDotNetCore/Queries/Internal/Parsing/FieldChainInheritanceRequirement.cs
 create mode 100644 src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldCategory.cs
 create mode 100644 src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainErrorFormatter.cs
 create mode 100644 src/JsonApiDotNetCore/Resources/SortExpressionLambdaConverter.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/WheelSortDefinition.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs

diff --git a/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs b/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
index 6c40c16b0f..83491d5c22 100644
--- a/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
+++ b/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
@@ -206,6 +206,61 @@ public IReadOnlySet<ResourceType> GetAllConcreteDerivedTypes()
         return _lazyAllConcreteDerivedTypes.Value;
     }
 
+    internal IReadOnlySet<AttrAttribute> GetAttributesInTypeOrDerived(string publicName)
+    {
+        return GetAttributesInTypeOrDerived(this, publicName);
+    }
+
+    private static IReadOnlySet<AttrAttribute> GetAttributesInTypeOrDerived(ResourceType resourceType, string publicName)
+    {
+        AttrAttribute? attribute = resourceType.FindAttributeByPublicName(publicName);
+
+        if (attribute != null)
+        {
+            return attribute.AsHashSet();
+        }
+
+        // Hiding base members using the 'new' keyword instead of 'override' (effectively breaking inheritance) is currently not supported.
+        // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/knowing-when-to-use-override-and-new-keywords
+        HashSet<AttrAttribute> attributesInDerivedTypes = new();
+
+        foreach (AttrAttribute attributeInDerivedType in resourceType.DirectlyDerivedTypes
+            .Select(derivedType => GetAttributesInTypeOrDerived(derivedType, publicName)).SelectMany(attributesInDerivedType => attributesInDerivedType))
+        {
+            attributesInDerivedTypes.Add(attributeInDerivedType);
+        }
+
+        return attributesInDerivedTypes;
+    }
+
+    internal IReadOnlySet<RelationshipAttribute> GetRelationshipsInTypeOrDerived(string publicName)
+    {
+        return GetRelationshipsInTypeOrDerived(this, publicName);
+    }
+
+    private static IReadOnlySet<RelationshipAttribute> GetRelationshipsInTypeOrDerived(ResourceType resourceType, string publicName)
+    {
+        RelationshipAttribute? relationship = resourceType.FindRelationshipByPublicName(publicName);
+
+        if (relationship != null)
+        {
+            return relationship.AsHashSet();
+        }
+
+        // Hiding base members using the 'new' keyword instead of 'override' (effectively breaking inheritance) is currently not supported.
+        // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/knowing-when-to-use-override-and-new-keywords
+        HashSet<RelationshipAttribute> relationshipsInDerivedTypes = new();
+
+        foreach (RelationshipAttribute relationshipInDerivedType in resourceType.DirectlyDerivedTypes
+            .Select(derivedType => GetRelationshipsInTypeOrDerived(derivedType, publicName))
+            .SelectMany(relationshipsInDerivedType => relationshipsInDerivedType))
+        {
+            relationshipsInDerivedTypes.Add(relationshipInDerivedType);
+        }
+
+        return relationshipsInDerivedTypes;
+    }
+
     public override string ToString()
     {
         return PublicName;
diff --git a/src/JsonApiDotNetCore/Configuration/IResourceGraph.cs b/src/JsonApiDotNetCore/Configuration/IResourceGraph.cs
index 9ccce6c60a..a98b74c3fe 100644
--- a/src/JsonApiDotNetCore/Configuration/IResourceGraph.cs
+++ b/src/JsonApiDotNetCore/Configuration/IResourceGraph.cs
@@ -54,7 +54,7 @@ ResourceType GetResourceType<TResource>()
     /// (TResource resource) => new { resource.Attribute1, resource.Relationship2 }
     /// ]]>
     /// </param>
-    IReadOnlyCollection<ResourceFieldAttribute> GetFields<TResource>(Expression<Func<TResource, dynamic?>> selector)
+    IReadOnlyCollection<ResourceFieldAttribute> GetFields<TResource>(Expression<Func<TResource, object?>> selector)
         where TResource : class, IIdentifiable;
 
     /// <summary>
@@ -68,7 +68,7 @@ IReadOnlyCollection<ResourceFieldAttribute> GetFields<TResource>(Expression<Func
     /// (TResource resource) => new { resource.attribute1, resource.Attribute2 }
     /// ]]>
     /// </param>
-    IReadOnlyCollection<AttrAttribute> GetAttributes<TResource>(Expression<Func<TResource, dynamic?>> selector)
+    IReadOnlyCollection<AttrAttribute> GetAttributes<TResource>(Expression<Func<TResource, object?>> selector)
         where TResource : class, IIdentifiable;
 
     /// <summary>
@@ -82,6 +82,6 @@ IReadOnlyCollection<AttrAttribute> GetAttributes<TResource>(Expression<Func<TRes
     /// (TResource resource) => new { resource.Relationship1, resource.Relationship2 }
     /// ]]>
     /// </param>
-    IReadOnlyCollection<RelationshipAttribute> GetRelationships<TResource>(Expression<Func<TResource, dynamic?>> selector)
+    IReadOnlyCollection<RelationshipAttribute> GetRelationships<TResource>(Expression<Func<TResource, object?>> selector)
         where TResource : class, IIdentifiable;
 }
diff --git a/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs b/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs
index d5acc8a1f9..6815fbf076 100644
--- a/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs
+++ b/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs
@@ -91,7 +91,7 @@ public ResourceType GetResourceType<TResource>()
     }
 
     /// <inheritdoc />
-    public IReadOnlyCollection<ResourceFieldAttribute> GetFields<TResource>(Expression<Func<TResource, dynamic?>> selector)
+    public IReadOnlyCollection<ResourceFieldAttribute> GetFields<TResource>(Expression<Func<TResource, object?>> selector)
         where TResource : class, IIdentifiable
     {
         ArgumentGuard.NotNull(selector, nameof(selector));
@@ -100,7 +100,7 @@ public IReadOnlyCollection<ResourceFieldAttribute> GetFields<TResource>(Expressi
     }
 
     /// <inheritdoc />
-    public IReadOnlyCollection<AttrAttribute> GetAttributes<TResource>(Expression<Func<TResource, dynamic?>> selector)
+    public IReadOnlyCollection<AttrAttribute> GetAttributes<TResource>(Expression<Func<TResource, object?>> selector)
         where TResource : class, IIdentifiable
     {
         ArgumentGuard.NotNull(selector, nameof(selector));
@@ -109,7 +109,7 @@ public IReadOnlyCollection<AttrAttribute> GetAttributes<TResource>(Expression<Fu
     }
 
     /// <inheritdoc />
-    public IReadOnlyCollection<RelationshipAttribute> GetRelationships<TResource>(Expression<Func<TResource, dynamic?>> selector)
+    public IReadOnlyCollection<RelationshipAttribute> GetRelationships<TResource>(Expression<Func<TResource, object?>> selector)
         where TResource : class, IIdentifiable
     {
         ArgumentGuard.NotNull(selector, nameof(selector));
@@ -117,7 +117,7 @@ public IReadOnlyCollection<RelationshipAttribute> GetRelationships<TResource>(Ex
         return FilterFields<TResource, RelationshipAttribute>(selector);
     }
 
-    private IReadOnlyCollection<TField> FilterFields<TResource, TField>(Expression<Func<TResource, dynamic?>> selector)
+    private IReadOnlyCollection<TField> FilterFields<TResource, TField>(Expression<Func<TResource, object?>> selector)
         where TResource : class, IIdentifiable
         where TField : ResourceFieldAttribute
     {
@@ -157,7 +157,7 @@ private IReadOnlyCollection<TKind> GetFieldsOfType<TResource, TKind>()
         return (IReadOnlyCollection<TKind>)resourceType.Fields;
     }
 
-    private IEnumerable<string> ToMemberNames<TResource>(Expression<Func<TResource, dynamic?>> selector)
+    private IEnumerable<string> ToMemberNames<TResource>(Expression<Func<TResource, object?>> selector)
     {
         Expression selectorBody = RemoveConvert(selector.Body);
 
diff --git a/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpressionExtensions.cs b/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpressionExtensions.cs
index f0e434cccd..53f9ff0eb6 100644
--- a/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpressionExtensions.cs
+++ b/src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpressionExtensions.cs
@@ -11,7 +11,7 @@ namespace JsonApiDotNetCore.Queries.Expressions;
 public static class SparseFieldSetExpressionExtensions
 {
     public static SparseFieldSetExpression? Including<TResource>(this SparseFieldSetExpression? sparseFieldSet,
-        Expression<Func<TResource, dynamic?>> fieldSelector, IResourceGraph resourceGraph)
+        Expression<Func<TResource, object?>> fieldSelector, IResourceGraph resourceGraph)
         where TResource : class, IIdentifiable
     {
         ArgumentGuard.NotNull(fieldSelector, nameof(fieldSelector));
@@ -39,7 +39,7 @@ public static class SparseFieldSetExpressionExtensions
     }
 
     public static SparseFieldSetExpression? Excluding<TResource>(this SparseFieldSetExpression? sparseFieldSet,
-        Expression<Func<TResource, dynamic?>> fieldSelector, IResourceGraph resourceGraph)
+        Expression<Func<TResource, object?>> fieldSelector, IResourceGraph resourceGraph)
         where TResource : class, IIdentifiable
     {
         ArgumentGuard.NotNull(fieldSelector, nameof(fieldSelector));
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/FieldChainInheritanceRequirement.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/FieldChainInheritanceRequirement.cs
new file mode 100644
index 0000000000..4b779d1ccd
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/FieldChainInheritanceRequirement.cs
@@ -0,0 +1,17 @@
+namespace JsonApiDotNetCore.Queries.Internal.Parsing;
+
+/// <summary>
+/// Indicates how to handle derived types when resolving resource field chains.
+/// </summary>
+internal enum FieldChainInheritanceRequirement
+{
+    /// <summary>
+    /// Do not consider derived types when resolving attributes or relationships.
+    /// </summary>
+    Disabled,
+
+    /// <summary>
+    /// Consider derived types when resolving attributes or relationships, but fail when multiple matches are found.
+    /// </summary>
+    RequireSingleMatch
+}
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs
index 5bd0a8d231..705f057bc5 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/FilterParser.cs
@@ -425,12 +425,14 @@ protected override IImmutableList<ResourceFieldAttribute> OnResolveFieldChain(st
     {
         if (chainRequirements == FieldChainRequirements.EndsInToMany)
         {
-            return ChainResolver.ResolveToOneChainEndingInToMany(_resourceTypeInScope!, path, _validateSingleFieldCallback);
+            return ChainResolver.ResolveToOneChainEndingInToMany(_resourceTypeInScope!, path, FieldChainInheritanceRequirement.Disabled,
+                _validateSingleFieldCallback);
         }
 
         if (chainRequirements == FieldChainRequirements.EndsInAttribute)
         {
-            return ChainResolver.ResolveToOneChainEndingInAttribute(_resourceTypeInScope!, path, _validateSingleFieldCallback);
+            return ChainResolver.ResolveToOneChainEndingInAttribute(_resourceTypeInScope!, path, FieldChainInheritanceRequirement.Disabled,
+                _validateSingleFieldCallback);
         }
 
         if (chainRequirements == FieldChainRequirements.EndsInToOne)
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
index a64f0b0b68..a453921989 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/IncludeParser.cs
@@ -11,6 +11,8 @@ namespace JsonApiDotNetCore.Queries.Internal.Parsing;
 [PublicAPI]
 public class IncludeParser : QueryExpressionParser
 {
+    private static readonly ResourceFieldChainErrorFormatter ErrorFormatter = new();
+
     public IncludeExpression Parse(string source, ResourceType resourceTypeInScope, int? maximumDepth)
     {
         ArgumentGuard.NotNull(resourceTypeInScope, nameof(resourceTypeInScope));
@@ -98,7 +100,7 @@ private ICollection<IncludeTreeNode> LookupRelationshipName(string relationshipN
         {
             // Depending on the left side of the include chain, we may match relationships anywhere in the resource type hierarchy.
             // This is compensated for when rendering the response, which substitutes relationships on base types with the derived ones.
-            ISet<RelationshipAttribute> relationships = GetRelationshipsInTypeOrDerived(parent.Relationship.RightType, relationshipName);
+            IReadOnlySet<RelationshipAttribute> relationships = parent.Relationship.RightType.GetRelationshipsInTypeOrDerived(relationshipName);
 
             if (relationships.Any())
             {
@@ -116,28 +118,6 @@ private ICollection<IncludeTreeNode> LookupRelationshipName(string relationshipN
         return children;
     }
 
-    private ISet<RelationshipAttribute> GetRelationshipsInTypeOrDerived(ResourceType resourceType, string relationshipName)
-    {
-        RelationshipAttribute? relationship = resourceType.FindRelationshipByPublicName(relationshipName);
-
-        if (relationship != null)
-        {
-            return relationship.AsHashSet();
-        }
-
-        // Hiding base members using the 'new' keyword instead of 'override' (effectively breaking inheritance) is currently not supported.
-        // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/knowing-when-to-use-override-and-new-keywords
-        HashSet<RelationshipAttribute> relationshipsInDerivedTypes = new();
-
-        foreach (ResourceType derivedType in resourceType.DirectlyDerivedTypes)
-        {
-            ISet<RelationshipAttribute> relationshipsInDerivedType = GetRelationshipsInTypeOrDerived(derivedType, relationshipName);
-            relationshipsInDerivedTypes.AddRange(relationshipsInDerivedType);
-        }
-
-        return relationshipsInDerivedTypes;
-    }
-
     private static void AssertRelationshipsFound(ISet<RelationshipAttribute> relationshipsFound, string relationshipName, ICollection<IncludeTreeNode> parents)
     {
         if (relationshipsFound.Any())
@@ -145,32 +125,15 @@ private static void AssertRelationshipsFound(ISet<RelationshipAttribute> relatio
             return;
         }
 
-        var messageBuilder = new StringBuilder();
-        messageBuilder.Append($"Relationship '{relationshipName}'");
-
         string[] parentPaths = parents.Select(parent => parent.Path).Distinct().Where(path => path != string.Empty).ToArray();
-
-        if (parentPaths.Length > 0)
-        {
-            messageBuilder.Append($" in '{parentPaths[0]}.{relationshipName}'");
-        }
+        string path = parentPaths.Length > 0 ? $"{parentPaths[0]}.{relationshipName}" : relationshipName;
 
         ResourceType[] parentResourceTypes = parents.Select(parent => parent.Relationship.RightType).Distinct().ToArray();
 
-        if (parentResourceTypes.Length == 1)
-        {
-            messageBuilder.Append($" does not exist on resource type '{parentResourceTypes[0].PublicName}'");
-        }
-        else
-        {
-            string typeNames = string.Join(", ", parentResourceTypes.Select(type => $"'{type.PublicName}'"));
-            messageBuilder.Append($" does not exist on any of the resource types {typeNames}");
-        }
-
-        bool hasDerived = parents.Any(parent => parent.Relationship.RightType.DirectlyDerivedTypes.Count > 0);
-        messageBuilder.Append(hasDerived ? " or any of its derived types." : ".");
+        bool hasDerivedTypes = parents.Any(parent => parent.Relationship.RightType.DirectlyDerivedTypes.Count > 0);
 
-        throw new QueryParseException(messageBuilder.ToString());
+        string message = ErrorFormatter.GetForNoneFound(ResourceFieldCategory.Relationship, relationshipName, path, parentResourceTypes, hasDerivedTypes);
+        throw new QueryParseException(message);
     }
 
     private static void AssertAtLeastOneCanBeIncluded(ISet<RelationshipAttribute> relationshipsFound, string relationshipName,
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldCategory.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldCategory.cs
new file mode 100644
index 0000000000..6630cf2767
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldCategory.cs
@@ -0,0 +1,8 @@
+namespace JsonApiDotNetCore.Queries.Internal.Parsing;
+
+internal enum ResourceFieldCategory
+{
+    Field,
+    Attribute,
+    Relationship
+}
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainErrorFormatter.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainErrorFormatter.cs
new file mode 100644
index 0000000000..e15b14893a
--- /dev/null
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainErrorFormatter.cs
@@ -0,0 +1,83 @@
+using System.Text;
+using JsonApiDotNetCore.Configuration;
+
+namespace JsonApiDotNetCore.Queries.Internal.Parsing;
+
+internal sealed class ResourceFieldChainErrorFormatter
+{
+    public string GetForNotFound(ResourceFieldCategory category, string publicName, string path, ResourceType resourceType,
+        FieldChainInheritanceRequirement inheritanceRequirement)
+    {
+        var builder = new StringBuilder();
+        WriteSource(category, publicName, builder);
+        WritePath(path, publicName, builder);
+
+        builder.Append($" does not exist on resource type '{resourceType.PublicName}'");
+
+        if (inheritanceRequirement != FieldChainInheritanceRequirement.Disabled && resourceType.DirectlyDerivedTypes.Any())
+        {
+            builder.Append(" or any of its derived types");
+        }
+
+        builder.Append('.');
+
+        return builder.ToString();
+    }
+
+    public string GetForMultipleMatches(ResourceFieldCategory category, string publicName, string path)
+    {
+        var builder = new StringBuilder();
+        WriteSource(category, publicName, builder);
+        WritePath(path, publicName, builder);
+
+        builder.Append(" is defined on multiple derived types.");
+
+        return builder.ToString();
+    }
+
+    public string GetForWrongFieldType(ResourceFieldCategory category, string publicName, string path, ResourceType resourceType, string expected)
+    {
+        var builder = new StringBuilder();
+        WriteSource(category, publicName, builder);
+        WritePath(path, publicName, builder);
+
+        builder.Append($" must be {expected} on resource type '{resourceType.PublicName}'.");
+
+        return builder.ToString();
+    }
+
+    public string GetForNoneFound(ResourceFieldCategory category, string publicName, string path, ICollection<ResourceType> parentResourceTypes,
+        bool hasDerivedTypes)
+    {
+        var builder = new StringBuilder();
+        WriteSource(category, publicName, builder);
+        WritePath(path, publicName, builder);
+
+        if (parentResourceTypes.Count == 1)
+        {
+            builder.Append($" does not exist on resource type '{parentResourceTypes.First().PublicName}'");
+        }
+        else
+        {
+            string typeNames = string.Join(", ", parentResourceTypes.Select(type => $"'{type.PublicName}'"));
+            builder.Append($" does not exist on any of the resource types {typeNames}");
+        }
+
+        builder.Append(hasDerivedTypes ? " or any of its derived types." : ".");
+
+        return builder.ToString();
+    }
+
+    private static void WriteSource(ResourceFieldCategory category, string publicName, StringBuilder builder)
+    {
+        builder.Append($"{category} '{publicName}'");
+    }
+
+    private static void WritePath(string path, string publicName, StringBuilder builder)
+    {
+        if (path != publicName)
+        {
+            builder.Append($" in '{path}'");
+        }
+    }
+}
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs
index 1b3ef7dcfe..4fb2632557 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/ResourceFieldChainResolver.cs
@@ -9,6 +9,8 @@ namespace JsonApiDotNetCore.Queries.Internal.Parsing;
 /// </summary>
 internal sealed class ResourceFieldChainResolver
 {
+    private static readonly ResourceFieldChainErrorFormatter ErrorFormatter = new();
+
     /// <summary>
     /// Resolves a chain of to-one relationships.
     /// <example>author</example>
@@ -24,7 +26,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChain(ResourceType res
 
         foreach (string publicName in path.Split("."))
         {
-            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path);
+            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path, FieldChainInheritanceRequirement.Disabled);
 
             validateCallback?.Invoke(toOneRelationship, nextResourceType, path);
 
@@ -48,7 +50,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToManyChain(ResourceType re
 
         foreach (string publicName in publicNameParts[..^1])
         {
-            RelationshipAttribute relationship = GetRelationship(publicName, nextResourceType, path);
+            RelationshipAttribute relationship = GetRelationship(publicName, nextResourceType, path, FieldChainInheritanceRequirement.Disabled);
 
             validateCallback?.Invoke(relationship, nextResourceType, path);
 
@@ -57,7 +59,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToManyChain(ResourceType re
         }
 
         string lastName = publicNameParts[^1];
-        RelationshipAttribute lastToManyRelationship = GetToManyRelationship(lastName, nextResourceType, path);
+        RelationshipAttribute lastToManyRelationship = GetToManyRelationship(lastName, nextResourceType, path, FieldChainInheritanceRequirement.Disabled);
 
         validateCallback?.Invoke(lastToManyRelationship, nextResourceType, path);
 
@@ -85,7 +87,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveRelationshipChain(ResourceT
 
         foreach (string publicName in path.Split("."))
         {
-            RelationshipAttribute relationship = GetRelationship(publicName, nextResourceType, path);
+            RelationshipAttribute relationship = GetRelationship(publicName, nextResourceType, path, FieldChainInheritanceRequirement.Disabled);
 
             validateCallback?.Invoke(relationship, nextResourceType, path);
 
@@ -104,7 +106,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveRelationshipChain(ResourceT
     /// <example>name</example>
     /// </summary>
     public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInAttribute(ResourceType resourceType, string path,
-        Action<ResourceFieldAttribute, ResourceType, string>? validateCallback = null)
+        FieldChainInheritanceRequirement inheritanceRequirement, Action<ResourceFieldAttribute, ResourceType, string>? validateCallback = null)
     {
         ImmutableArray<ResourceFieldAttribute>.Builder chainBuilder = ImmutableArray.CreateBuilder<ResourceFieldAttribute>();
 
@@ -113,7 +115,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInAttribute
 
         foreach (string publicName in publicNameParts[..^1])
         {
-            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path);
+            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path, inheritanceRequirement);
 
             validateCallback?.Invoke(toOneRelationship, nextResourceType, path);
 
@@ -122,7 +124,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInAttribute
         }
 
         string lastName = publicNameParts[^1];
-        AttrAttribute lastAttribute = GetAttribute(lastName, nextResourceType, path);
+        AttrAttribute lastAttribute = GetAttribute(lastName, nextResourceType, path, inheritanceRequirement);
 
         validateCallback?.Invoke(lastAttribute, nextResourceType, path);
 
@@ -140,7 +142,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInAttribute
     /// </example>
     /// </summary>
     public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInToMany(ResourceType resourceType, string path,
-        Action<ResourceFieldAttribute, ResourceType, string>? validateCallback = null)
+        FieldChainInheritanceRequirement inheritanceRequirement, Action<ResourceFieldAttribute, ResourceType, string>? validateCallback = null)
     {
         ImmutableArray<ResourceFieldAttribute>.Builder chainBuilder = ImmutableArray.CreateBuilder<ResourceFieldAttribute>();
 
@@ -149,7 +151,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInToMany(Re
 
         foreach (string publicName in publicNameParts[..^1])
         {
-            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path);
+            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path, inheritanceRequirement);
 
             validateCallback?.Invoke(toOneRelationship, nextResourceType, path);
 
@@ -159,7 +161,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInToMany(Re
 
         string lastName = publicNameParts[^1];
 
-        RelationshipAttribute toManyRelationship = GetToManyRelationship(lastName, nextResourceType, path);
+        RelationshipAttribute toManyRelationship = GetToManyRelationship(lastName, nextResourceType, path, inheritanceRequirement);
 
         validateCallback?.Invoke(toManyRelationship, nextResourceType, path);
 
@@ -186,7 +188,7 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInAttribute
 
         foreach (string publicName in publicNameParts[..^1])
         {
-            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path);
+            RelationshipAttribute toOneRelationship = GetToOneRelationship(publicName, nextResourceType, path, FieldChainInheritanceRequirement.Disabled);
 
             validateCallback?.Invoke(toOneRelationship, nextResourceType, path);
 
@@ -199,9 +201,10 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInAttribute
 
         if (lastField is HasManyAttribute)
         {
-            throw new QueryParseException(path == lastName
-                ? $"Field '{lastName}' must be an attribute or a to-one relationship on resource type '{nextResourceType.PublicName}'."
-                : $"Field '{lastName}' in '{path}' must be an attribute or a to-one relationship on resource type '{nextResourceType.PublicName}'.");
+            string message = ErrorFormatter.GetForWrongFieldType(ResourceFieldCategory.Field, lastName, path, nextResourceType,
+                "an attribute or a to-one relationship");
+
+            throw new QueryParseException(message);
         }
 
         validateCallback?.Invoke(lastField, nextResourceType, path);
@@ -210,60 +213,75 @@ public IImmutableList<ResourceFieldAttribute> ResolveToOneChainEndingInAttribute
         return chainBuilder.ToImmutable();
     }
 
-    private RelationshipAttribute GetRelationship(string publicName, ResourceType resourceType, string path)
+    private RelationshipAttribute GetRelationship(string publicName, ResourceType resourceType, string path,
+        FieldChainInheritanceRequirement inheritanceRequirement)
     {
-        RelationshipAttribute? relationship = resourceType.FindRelationshipByPublicName(publicName);
+        IReadOnlyCollection<RelationshipAttribute> relationships = inheritanceRequirement == FieldChainInheritanceRequirement.Disabled
+            ? resourceType.FindRelationshipByPublicName(publicName)?.AsArray() ?? Array.Empty<RelationshipAttribute>()
+            : resourceType.GetRelationshipsInTypeOrDerived(publicName);
 
-        if (relationship == null)
+        if (relationships.Count == 0)
         {
-            throw new QueryParseException(path == publicName
-                ? $"Relationship '{publicName}' does not exist on resource type '{resourceType.PublicName}'."
-                : $"Relationship '{publicName}' in '{path}' does not exist on resource type '{resourceType.PublicName}'.");
+            string message = ErrorFormatter.GetForNotFound(ResourceFieldCategory.Relationship, publicName, path, resourceType, inheritanceRequirement);
+            throw new QueryParseException(message);
         }
 
-        return relationship;
+        if (inheritanceRequirement == FieldChainInheritanceRequirement.RequireSingleMatch && relationships.Count > 1)
+        {
+            string message = ErrorFormatter.GetForMultipleMatches(ResourceFieldCategory.Relationship, publicName, path);
+            throw new QueryParseException(message);
+        }
+
+        return relationships.First();
     }
 
-    private RelationshipAttribute GetToManyRelationship(string publicName, ResourceType resourceType, string path)
+    private RelationshipAttribute GetToManyRelationship(string publicName, ResourceType resourceType, string path,
+        FieldChainInheritanceRequirement inheritanceRequirement)
     {
-        RelationshipAttribute relationship = GetRelationship(publicName, resourceType, path);
+        RelationshipAttribute relationship = GetRelationship(publicName, resourceType, path, inheritanceRequirement);
 
         if (relationship is not HasManyAttribute)
         {
-            throw new QueryParseException(path == publicName
-                ? $"Relationship '{publicName}' must be a to-many relationship on resource type '{resourceType.PublicName}'."
-                : $"Relationship '{publicName}' in '{path}' must be a to-many relationship on resource type '{resourceType.PublicName}'.");
+            string message = ErrorFormatter.GetForWrongFieldType(ResourceFieldCategory.Relationship, publicName, path, resourceType, "a to-many relationship");
+            throw new QueryParseException(message);
         }
 
         return relationship;
     }
 
-    private RelationshipAttribute GetToOneRelationship(string publicName, ResourceType resourceType, string path)
+    private RelationshipAttribute GetToOneRelationship(string publicName, ResourceType resourceType, string path,
+        FieldChainInheritanceRequirement inheritanceRequirement)
     {
-        RelationshipAttribute relationship = GetRelationship(publicName, resourceType, path);
+        RelationshipAttribute relationship = GetRelationship(publicName, resourceType, path, inheritanceRequirement);
 
         if (relationship is not HasOneAttribute)
         {
-            throw new QueryParseException(path == publicName
-                ? $"Relationship '{publicName}' must be a to-one relationship on resource type '{resourceType.PublicName}'."
-                : $"Relationship '{publicName}' in '{path}' must be a to-one relationship on resource type '{resourceType.PublicName}'.");
+            string message = ErrorFormatter.GetForWrongFieldType(ResourceFieldCategory.Relationship, publicName, path, resourceType, "a to-one relationship");
+            throw new QueryParseException(message);
         }
 
         return relationship;
     }
 
-    private AttrAttribute GetAttribute(string publicName, ResourceType resourceType, string path)
+    private AttrAttribute GetAttribute(string publicName, ResourceType resourceType, string path, FieldChainInheritanceRequirement inheritanceRequirement)
     {
-        AttrAttribute? attribute = resourceType.FindAttributeByPublicName(publicName);
+        IReadOnlyCollection<AttrAttribute> attributes = inheritanceRequirement == FieldChainInheritanceRequirement.Disabled
+            ? resourceType.FindAttributeByPublicName(publicName)?.AsArray() ?? Array.Empty<AttrAttribute>()
+            : resourceType.GetAttributesInTypeOrDerived(publicName);
+
+        if (attributes.Count == 0)
+        {
+            string message = ErrorFormatter.GetForNotFound(ResourceFieldCategory.Attribute, publicName, path, resourceType, inheritanceRequirement);
+            throw new QueryParseException(message);
+        }
 
-        if (attribute == null)
+        if (inheritanceRequirement == FieldChainInheritanceRequirement.RequireSingleMatch && attributes.Count > 1)
         {
-            throw new QueryParseException(path == publicName
-                ? $"Attribute '{publicName}' does not exist on resource type '{resourceType.PublicName}'."
-                : $"Attribute '{publicName}' in '{path}' does not exist on resource type '{resourceType.PublicName}'.");
+            string message = ErrorFormatter.GetForMultipleMatches(ResourceFieldCategory.Attribute, publicName, path);
+            throw new QueryParseException(message);
         }
 
-        return attribute;
+        return attributes.First();
     }
 
     public ResourceFieldAttribute GetField(string publicName, ResourceType resourceType, string path)
@@ -272,9 +290,10 @@ public ResourceFieldAttribute GetField(string publicName, ResourceType resourceT
 
         if (field == null)
         {
-            throw new QueryParseException(path == publicName
-                ? $"Field '{publicName}' does not exist on resource type '{resourceType.PublicName}'."
-                : $"Field '{publicName}' in '{path}' does not exist on resource type '{resourceType.PublicName}'.");
+            string message = ErrorFormatter.GetForNotFound(ResourceFieldCategory.Field, publicName, path, resourceType,
+                FieldChainInheritanceRequirement.Disabled);
+
+            throw new QueryParseException(message);
         }
 
         return field;
diff --git a/src/JsonApiDotNetCore/Queries/Internal/Parsing/SortParser.cs b/src/JsonApiDotNetCore/Queries/Internal/Parsing/SortParser.cs
index 38a263e063..84782c2b3e 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/Parsing/SortParser.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/Parsing/SortParser.cs
@@ -74,14 +74,40 @@ protected SortElementExpression ParseSortElement()
 
     protected override IImmutableList<ResourceFieldAttribute> OnResolveFieldChain(string path, FieldChainRequirements chainRequirements)
     {
+        // An attribute or relationship name usually matches a single field, even when overridden in derived types.
+        // But in the following case, two attributes are matched on GET /shoppingBaskets?sort=bonusPoints:
+        //
+        // public abstract class ShoppingBasket : Identifiable<long>
+        // {
+        // }
+        //
+        // public sealed class SilverShoppingBasket : ShoppingBasket
+        // {
+        //     [Attr]
+        //     public short BonusPoints { get; set; }
+        // }
+        //
+        // public sealed class PlatinumShoppingBasket : ShoppingBasket
+        // {
+        //     [Attr]
+        //     public long BonusPoints { get; set; }
+        // }
+        //
+        // In this case there are two distinct BonusPoints fields (with different data types). And the sort order depends
+        // on which attribute is used.
+        //
+        // Because there is no syntax to pick one, we fail with an error. We could add such optional upcast syntax
+        // (which would be required in this case) in the future to make it work, if desired.
+
         if (chainRequirements == FieldChainRequirements.EndsInToMany)
         {
-            return ChainResolver.ResolveToOneChainEndingInToMany(_resourceTypeInScope!, path);
+            return ChainResolver.ResolveToOneChainEndingInToMany(_resourceTypeInScope!, path, FieldChainInheritanceRequirement.RequireSingleMatch);
         }
 
         if (chainRequirements == FieldChainRequirements.EndsInAttribute)
         {
-            return ChainResolver.ResolveToOneChainEndingInAttribute(_resourceTypeInScope!, path, _validateSingleFieldCallback);
+            return ChainResolver.ResolveToOneChainEndingInAttribute(_resourceTypeInScope!, path, FieldChainInheritanceRequirement.RequireSingleMatch,
+                _validateSingleFieldCallback);
         }
 
         throw new InvalidOperationException($"Unexpected combination of chain requirement flags '{chainRequirements}'.");
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs
index de80d8a6ff..d04ff57e9d 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/QueryClauseBuilder.cs
@@ -1,6 +1,7 @@
 using System.Linq.Expressions;
 using System.Reflection;
 using JsonApiDotNetCore.Queries.Expressions;
+using JsonApiDotNetCore.Resources.Annotations;
 
 namespace JsonApiDotNetCore.Queries.Internal.QueryableBuilding;
 
@@ -59,26 +60,26 @@ public override Expression VisitCount(CountExpression expression, TArgument argu
     }
 
     public override Expression VisitResourceFieldChain(ResourceFieldChainExpression expression, TArgument argument)
-    {
-        string[] components = expression.Fields.Select(field => field.Property.Name).ToArray();
-
-        return CreatePropertyExpressionFromComponents(LambdaScope.Accessor, components);
-    }
-
-    private static MemberExpression CreatePropertyExpressionFromComponents(Expression source, IEnumerable<string> components)
     {
         MemberExpression? property = null;
 
-        foreach (string propertyName in components)
+        foreach (ResourceFieldAttribute field in expression.Fields)
         {
-            Type parentType = property == null ? source.Type : property.Type;
+            Expression parentAccessor = property ?? LambdaScope.Accessor;
+            Type propertyType = field.Property.DeclaringType!;
+            string propertyName = field.Property.Name;
+
+            bool requiresUpCast = parentAccessor.Type != propertyType && parentAccessor.Type.IsAssignableFrom(propertyType);
+            Type parentType = requiresUpCast ? propertyType : parentAccessor.Type;
 
             if (parentType.GetProperty(propertyName) == null)
             {
                 throw new InvalidOperationException($"Type '{parentType.Name}' does not contain a property named '{propertyName}'.");
             }
 
-            property = property == null ? Expression.Property(source, propertyName) : Expression.Property(property, propertyName);
+            property = requiresUpCast
+                ? Expression.MakeMemberAccess(Expression.Convert(parentAccessor, propertyType), field.Property)
+                : Expression.Property(parentAccessor, propertyName);
         }
 
         return property!;
diff --git a/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs b/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs
index 99f575a293..0050886112 100644
--- a/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs
+++ b/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs
@@ -1,11 +1,14 @@
 using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Linq.Expressions;
+using System.Net;
 using JetBrains.Annotations;
 using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
 using JsonApiDotNetCore.Middleware;
 using JsonApiDotNetCore.Queries.Expressions;
 using JsonApiDotNetCore.Resources.Annotations;
+using JsonApiDotNetCore.Serialization.Objects;
 
 namespace JsonApiDotNetCore.Resources;
 
@@ -54,8 +57,9 @@ public virtual IImmutableSet<IncludeElementExpression> OnApplyIncludes(IImmutabl
     /// <code><![CDATA[
     /// var sort = CreateSortExpressionFromLambda(new PropertySortOrder
     /// {
-    ///     (model => model.CreatedAt, ListSortDirection.Ascending),
-    ///     (model => model.Password, ListSortDirection.Descending)
+    ///     (blog => blog.Author.Name.LastName, ListSortDirection.Ascending),
+    ///     (blog => blog.Posts.Count, ListSortDirection.Descending),
+    ///     (blog => blog.Title, ListSortDirection.Ascending)
     /// });
     /// ]]></code>
     /// </example>
@@ -64,14 +68,26 @@ protected SortExpression CreateSortExpressionFromLambda(PropertySortOrder keySel
         ArgumentGuard.NotNullNorEmpty(keySelectors, nameof(keySelectors));
 
         ImmutableArray<SortElementExpression>.Builder elementsBuilder = ImmutableArray.CreateBuilder<SortElementExpression>(keySelectors.Count);
+        var lambdaConverter = new SortExpressionLambdaConverter(ResourceGraph);
 
-        foreach ((Expression<Func<TResource, dynamic?>> keySelector, ListSortDirection sortDirection) in keySelectors)
+        foreach ((Expression<Func<TResource, object?>> keySelector, ListSortDirection sortDirection) in keySelectors)
         {
-            bool isAscending = sortDirection == ListSortDirection.Ascending;
-            AttrAttribute attribute = ResourceGraph.GetAttributes(keySelector).Single();
-
-            var sortElement = new SortElementExpression(new ResourceFieldChainExpression(attribute), isAscending);
-            elementsBuilder.Add(sortElement);
+            try
+            {
+                SortElementExpression sortElement = lambdaConverter.FromLambda(keySelector, sortDirection);
+                elementsBuilder.Add(sortElement);
+            }
+            catch (InvalidOperationException exception)
+            {
+                throw new JsonApiException(new ErrorObject(HttpStatusCode.InternalServerError)
+                {
+                    Title = "Invalid lambda expression for sorting from resource definition. " +
+                        "It should select a property that is exposed as an attribute, or a to-many relationship followed by Count(). " +
+                        "The property can be preceded by a path of to-one relationships. " +
+                        "Examples: 'blog => blog.Title', 'blog => blog.Posts.Count', 'blog => blog.Author.Name.LastName'.",
+                    Detail = $"The lambda expression '{keySelector}' is invalid. {exception.Message}"
+                }, exception);
+            }
         }
 
         return new SortExpression(elementsBuilder.ToImmutable());
@@ -161,7 +177,7 @@ public virtual void OnSerialize(TResource resource)
     /// This is an alias type intended to simplify the implementation's method signature. See <see cref="CreateSortExpressionFromLambda" /> for usage
     /// details.
     /// </summary>
-    public sealed class PropertySortOrder : List<(Expression<Func<TResource, dynamic?>> KeySelector, ListSortDirection SortDirection)>
+    public sealed class PropertySortOrder : List<(Expression<Func<TResource, object?>> KeySelector, ListSortDirection SortDirection)>
     {
     }
 }
diff --git a/src/JsonApiDotNetCore/Resources/SortExpressionLambdaConverter.cs b/src/JsonApiDotNetCore/Resources/SortExpressionLambdaConverter.cs
new file mode 100644
index 0000000000..3736fff6d9
--- /dev/null
+++ b/src/JsonApiDotNetCore/Resources/SortExpressionLambdaConverter.cs
@@ -0,0 +1,167 @@
+using System.Collections.Immutable;
+using System.ComponentModel;
+using System.Linq.Expressions;
+using System.Reflection;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Queries.Expressions;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCore.Resources;
+
+internal sealed class SortExpressionLambdaConverter
+{
+    private readonly IResourceGraph _resourceGraph;
+    private readonly IList<ResourceFieldAttribute> _fields = new List<ResourceFieldAttribute>();
+
+    public SortExpressionLambdaConverter(IResourceGraph resourceGraph)
+    {
+        ArgumentGuard.NotNull(resourceGraph, nameof(resourceGraph));
+
+        _resourceGraph = resourceGraph;
+    }
+
+    public SortElementExpression FromLambda<TResource>(Expression<Func<TResource, object?>> keySelector, ListSortDirection sortDirection)
+    {
+        ArgumentGuard.NotNull(keySelector, nameof(keySelector));
+
+        _fields.Clear();
+
+        Expression lambdaBodyExpression = SkipConvert(keySelector.Body);
+        (Expression? expression, bool isCount) = TryReadCount(lambdaBodyExpression);
+
+        if (expression != null)
+        {
+            expression = SkipConvert(expression);
+            expression = isCount ? ReadToManyRelationship(expression) : ReadAttribute(expression);
+
+            while (expression != null)
+            {
+                expression = SkipConvert(expression);
+
+                if (IsLambdaParameter(expression, keySelector.Parameters[0]))
+                {
+                    return ToSortElement(isCount, sortDirection);
+                }
+
+                expression = ReadToOneRelationship(expression);
+            }
+        }
+
+        throw new InvalidOperationException($"Unsupported expression body '{lambdaBodyExpression}'.");
+    }
+
+    private static Expression SkipConvert(Expression expression)
+    {
+        Expression inner = expression;
+
+        while (true)
+        {
+            if (inner is UnaryExpression { NodeType: ExpressionType.Convert or ExpressionType.TypeAs } unary)
+            {
+                inner = unary.Operand;
+            }
+            else
+            {
+                return inner;
+            }
+        }
+    }
+
+    private static (Expression? innerExpression, bool isCount) TryReadCount(Expression expression)
+    {
+        if (expression is MethodCallExpression methodCallExpression && methodCallExpression.Method.Name == "Count")
+        {
+            if (methodCallExpression.Arguments.Count <= 1)
+            {
+                return (methodCallExpression.Arguments[0], true);
+            }
+
+            throw new InvalidOperationException("Count method that takes a predicate is not supported.");
+        }
+
+        if (expression is MemberExpression memberExpression)
+        {
+            if (memberExpression.Member.MemberType == MemberTypes.Property && memberExpression.Member.Name is "Count" or "Length")
+            {
+                if (memberExpression.Member.GetCustomAttribute<AttrAttribute>() == null)
+                {
+                    return (memberExpression.Expression, true);
+                }
+            }
+
+            return (memberExpression, false);
+        }
+
+        return (null, false);
+    }
+
+    private Expression? ReadToManyRelationship(Expression expression)
+    {
+        if (expression is MemberExpression memberExpression)
+        {
+            ResourceType resourceType = _resourceGraph.GetResourceType(memberExpression.Member.DeclaringType!);
+            RelationshipAttribute? relationship = resourceType.FindRelationshipByPropertyName(memberExpression.Member.Name);
+
+            if (relationship is HasManyAttribute)
+            {
+                _fields.Insert(0, relationship);
+                return memberExpression.Expression;
+            }
+        }
+
+        throw new InvalidOperationException($"Expected property for JSON:API to-many relationship, but found '{expression}'.");
+    }
+
+    private Expression? ReadAttribute(Expression expression)
+    {
+        if (expression is MemberExpression memberExpression)
+        {
+            ResourceType resourceType = _resourceGraph.GetResourceType(memberExpression.Member.DeclaringType!);
+            AttrAttribute? attribute = resourceType.FindAttributeByPropertyName(memberExpression.Member.Name);
+
+            if (attribute != null)
+            {
+                _fields.Insert(0, attribute);
+                return memberExpression.Expression;
+            }
+        }
+
+        throw new InvalidOperationException($"Expected property for JSON:API attribute, but found '{expression}'.");
+    }
+
+    private Expression? ReadToOneRelationship(Expression expression)
+    {
+        if (expression is MemberExpression memberExpression)
+        {
+            ResourceType resourceType = _resourceGraph.GetResourceType(memberExpression.Member.DeclaringType!);
+            RelationshipAttribute? relationship = resourceType.FindRelationshipByPropertyName(memberExpression.Member.Name);
+
+            if (relationship is HasOneAttribute)
+            {
+                _fields.Insert(0, relationship);
+                return memberExpression.Expression;
+            }
+        }
+
+        throw new InvalidOperationException($"Expected property for JSON:API to-one relationship, but found '{expression}'.");
+    }
+
+    private static bool IsLambdaParameter(Expression expression, ParameterExpression lambdaParameter)
+    {
+        return expression is ParameterExpression parameterExpression && parameterExpression.Name == lambdaParameter.Name;
+    }
+
+    private SortElementExpression ToSortElement(bool isCount, ListSortDirection sortDirection)
+    {
+        var chain = new ResourceFieldChainExpression(_fields.ToImmutableArray());
+        bool isAscending = sortDirection == ListSortDirection.Ascending;
+
+        if (isCount)
+        {
+            var countExpression = new CountExpression(chain);
+            return new SortElementExpression(countExpression, isAscending);
+        }
+
+        return new SortElementExpression(chain, isAscending);
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs
index c1be948c35..f5f0e55764 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Man.cs
@@ -10,6 +10,9 @@ public sealed class Man : Human
     [Attr]
     public bool HasBeard { get; set; }
 
+    [Attr]
+    public int Age { get; set; }
+
     [HasOne]
     public Woman? Wife { get; set; }
 
@@ -18,4 +21,7 @@ public sealed class Man : Human
 
     [HasMany]
     public ISet<Man> SameGenderFriends { get; set; } = new HashSet<Man>();
+
+    [HasMany]
+    public ISet<Man> DrinkingBuddies { get; set; } = new HashSet<Man>();
 }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs
index a7e762514a..8e1044b2de 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/QueryStrings/Woman.cs
@@ -10,6 +10,9 @@ public sealed class Woman : Human
     [Attr]
     public string MaidenName { get; set; } = null!;
 
+    [Attr]
+    public int Age { get; set; }
+
     [HasOne]
     public Man? Husband { get; set; }
 
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
index ed6897c7c2..c6753bf26e 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
@@ -35,8 +35,14 @@ protected ResourceInheritanceTests(IntegrationTestContext<TestableStartup<TDbCon
         testContext.UseController<ChromeWheelsController>();
         testContext.UseController<CarbonWheelsController>();
 
+        testContext.ConfigureServicesAfterStartup(services =>
+        {
+            services.AddResourceDefinition<WheelSortDefinition>();
+        });
+
         var options = (JsonApiOptions)testContext.Factory.Services.GetRequiredService<IJsonApiOptions>();
         options.UseRelativeLinks = true;
+        options.AllowUnknownQueryStringParameters = true;
     }
 
     [Fact]
@@ -1824,4 +1830,291 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
 
         responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "cars" && resource.Id == car3.StringId);
     }
+
+    [Fact]
+    public async Task Can_sort_on_derived_attribute_at_abstract_endpoint()
+    {
+        // Arrange
+        Bike bike1 = _fakers.Bike.Generate();
+        bike1.GearCount = 3;
+
+        Bike bike2 = _fakers.Bike.Generate();
+        bike2.GearCount = 1;
+
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.GearCount = 2;
+
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike1, bike2, tandem, car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/vehicles?sort=gearCount";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue[0].Type.Should().Be("bikes");
+        responseDocument.Data.ManyValue[0].Id.Should().Be(bike2.StringId);
+
+        responseDocument.Data.ManyValue[1].Type.Should().Be("tandems");
+        responseDocument.Data.ManyValue[1].Id.Should().Be(tandem.StringId);
+
+        responseDocument.Data.ManyValue[2].Type.Should().Be("bikes");
+        responseDocument.Data.ManyValue[2].Id.Should().Be(bike1.StringId);
+
+        responseDocument.Data.ManyValue[3].Type.Should().Be("cars");
+        responseDocument.Data.ManyValue[3].Id.Should().Be(car.StringId);
+    }
+
+    [Fact]
+    public async Task Can_sort_on_derived_attribute_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Bike bike = _fakers.Bike.Generate();
+
+        Tandem tandem1 = _fakers.Tandem.Generate();
+        tandem1.PassengerCount = 2;
+
+        Tandem tandem2 = _fakers.Tandem.Generate();
+        tandem2.PassengerCount = 4;
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(bike, tandem1, tandem2);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/bikes?sort=-passengerCount";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(3);
+
+        responseDocument.Data.ManyValue[0].Type.Should().Be("bikes");
+        responseDocument.Data.ManyValue[0].Id.Should().Be(bike.StringId);
+
+        responseDocument.Data.ManyValue[1].Type.Should().Be("tandems");
+        responseDocument.Data.ManyValue[1].Id.Should().Be(tandem2.StringId);
+
+        responseDocument.Data.ManyValue[2].Type.Should().Be("tandems");
+        responseDocument.Data.ManyValue[2].Id.Should().Be(tandem1.StringId);
+    }
+
+    [Fact]
+    public async Task Can_sort_on_derived_relationship_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Car car1 = _fakers.Car.Generate();
+        car1.Engine = _fakers.GasolineEngine.Generate();
+        ((GasolineEngine)car1.Engine).Cylinders = _fakers.Cylinder.Generate(2).ToHashSet();
+
+        Car car2 = _fakers.Car.Generate();
+        car2.Engine = _fakers.DieselEngine.Generate();
+
+        Car car3 = _fakers.Car.Generate();
+        car3.Engine = _fakers.GasolineEngine.Generate();
+        ((GasolineEngine)car3.Engine).Cylinders = _fakers.Cylinder.Generate(4).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Vehicles.AddRange(car1, car2, car3);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/cars?sort=-count(engine.cylinders)";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(3);
+
+        responseDocument.Data.ManyValue[0].Type.Should().Be("cars");
+        responseDocument.Data.ManyValue[0].Id.Should().Be(car3.StringId);
+
+        responseDocument.Data.ManyValue[1].Type.Should().Be("cars");
+        responseDocument.Data.ManyValue[1].Id.Should().Be(car1.StringId);
+
+        responseDocument.Data.ManyValue[2].Type.Should().Be("cars");
+        responseDocument.Data.ManyValue[2].Id.Should().Be(car2.StringId);
+    }
+
+    [Fact]
+    public async Task Cannot_sort_on_ambiguous_derived_attribute()
+    {
+        // Arrange
+        const string route = "/cars?sort=engine.serialCode";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.BadRequest);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.BadRequest);
+        error.Title.Should().Be("The specified sort is invalid.");
+        error.Detail.Should().Be("Attribute 'serialCode' in 'engine.serialCode' is defined on multiple derived types.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Parameter.Should().Be("sort");
+    }
+
+    [Fact]
+    public async Task Cannot_sort_on_ambiguous_derived_relationship()
+    {
+        // Arrange
+        const string route = "/vehicles?sort=count(features)";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.BadRequest);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.BadRequest);
+        error.Title.Should().Be("The specified sort is invalid.");
+        error.Detail.Should().Be("Relationship 'features' is defined on multiple derived types.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Parameter.Should().Be("sort");
+    }
+
+    [Fact]
+    public async Task Can_sort_on_derived_attribute_from_resource_definition_using_expression_syntax()
+    {
+        // Arrange
+        ChromeWheel chromeWheel1 = _fakers.ChromeWheel.Generate();
+        chromeWheel1.PaintColor = "blue";
+        chromeWheel1.Vehicle = _fakers.Car.Generate();
+        ((Car)chromeWheel1.Vehicle).Engine = _fakers.GasolineEngine.Generate();
+        ((GasolineEngine)((Car)chromeWheel1.Vehicle).Engine).Cylinders = _fakers.Cylinder.Generate(2).ToHashSet();
+
+        ChromeWheel chromeWheel2 = _fakers.ChromeWheel.Generate();
+        chromeWheel2.PaintColor = "blue";
+        chromeWheel2.Vehicle = _fakers.Car.Generate();
+        ((Car)chromeWheel2.Vehicle).Engine = _fakers.GasolineEngine.Generate();
+        ((GasolineEngine)((Car)chromeWheel2.Vehicle).Engine).Cylinders = _fakers.Cylinder.Generate(1).ToHashSet();
+
+        ChromeWheel chromeWheel3 = _fakers.ChromeWheel.Generate();
+        chromeWheel3.PaintColor = "black";
+
+        CarbonWheel carbonWheel1 = _fakers.CarbonWheel.Generate();
+        carbonWheel1.HasTube = false;
+
+        CarbonWheel carbonWheel2 = _fakers.CarbonWheel.Generate();
+        carbonWheel2.HasTube = true;
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Wheels.AddRange(chromeWheel1, chromeWheel2, chromeWheel3, carbonWheel1, carbonWheel2);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/wheels?autoSort=expr";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(5);
+
+        responseDocument.Data.ManyValue[0].Type.Should().Be("chromeWheels");
+        responseDocument.Data.ManyValue[0].Id.Should().Be(chromeWheel3.StringId);
+
+        responseDocument.Data.ManyValue[1].Type.Should().Be("chromeWheels");
+        responseDocument.Data.ManyValue[1].Id.Should().Be(chromeWheel2.StringId);
+
+        responseDocument.Data.ManyValue[2].Type.Should().Be("chromeWheels");
+        responseDocument.Data.ManyValue[2].Id.Should().Be(chromeWheel1.StringId);
+
+        responseDocument.Data.ManyValue[3].Type.Should().Be("carbonWheels");
+        responseDocument.Data.ManyValue[3].Id.Should().Be(carbonWheel2.StringId);
+
+        responseDocument.Data.ManyValue[4].Type.Should().Be("carbonWheels");
+        responseDocument.Data.ManyValue[4].Id.Should().Be(carbonWheel1.StringId);
+    }
+
+    [Fact]
+    public async Task Can_sort_on_derived_attribute_from_resource_definition_using_lambda_syntax()
+    {
+        // Arrange
+        ChromeWheel chromeWheel1 = _fakers.ChromeWheel.Generate();
+        chromeWheel1.PaintColor = "blue";
+        chromeWheel1.Vehicle = _fakers.Car.Generate();
+        ((Car)chromeWheel1.Vehicle).Engine = _fakers.GasolineEngine.Generate();
+        ((GasolineEngine)((Car)chromeWheel1.Vehicle).Engine).Cylinders = _fakers.Cylinder.Generate(2).ToHashSet();
+
+        ChromeWheel chromeWheel2 = _fakers.ChromeWheel.Generate();
+        chromeWheel2.PaintColor = "blue";
+        chromeWheel2.Vehicle = _fakers.Car.Generate();
+        ((Car)chromeWheel2.Vehicle).Engine = _fakers.GasolineEngine.Generate();
+        ((GasolineEngine)((Car)chromeWheel2.Vehicle).Engine).Cylinders = _fakers.Cylinder.Generate(1).ToHashSet();
+
+        ChromeWheel chromeWheel3 = _fakers.ChromeWheel.Generate();
+        chromeWheel3.PaintColor = "black";
+
+        CarbonWheel carbonWheel1 = _fakers.CarbonWheel.Generate();
+        carbonWheel1.HasTube = false;
+
+        CarbonWheel carbonWheel2 = _fakers.CarbonWheel.Generate();
+        carbonWheel2.HasTube = true;
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            await dbContext.ClearTableAsync<Vehicle>();
+            dbContext.Wheels.AddRange(chromeWheel1, chromeWheel2, chromeWheel3, carbonWheel1, carbonWheel2);
+            await dbContext.SaveChangesAsync();
+        });
+
+        const string route = "/wheels?autoSort=lambda";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(5);
+
+        responseDocument.Data.ManyValue[0].Type.Should().Be("chromeWheels");
+        responseDocument.Data.ManyValue[0].Id.Should().Be(chromeWheel3.StringId);
+
+        responseDocument.Data.ManyValue[1].Type.Should().Be("chromeWheels");
+        responseDocument.Data.ManyValue[1].Id.Should().Be(chromeWheel2.StringId);
+
+        responseDocument.Data.ManyValue[2].Type.Should().Be("chromeWheels");
+        responseDocument.Data.ManyValue[2].Id.Should().Be(chromeWheel1.StringId);
+
+        responseDocument.Data.ManyValue[3].Type.Should().Be("carbonWheels");
+        responseDocument.Data.ManyValue[3].Id.Should().Be(carbonWheel2.StringId);
+
+        responseDocument.Data.ManyValue[4].Type.Should().Be("carbonWheels");
+        responseDocument.Data.ManyValue[4].Id.Should().Be(carbonWheel1.StringId);
+    }
 }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/WheelSortDefinition.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/WheelSortDefinition.cs
new file mode 100644
index 0000000000..f727c011df
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/WheelSortDefinition.cs
@@ -0,0 +1,69 @@
+using System.Collections.Immutable;
+using System.ComponentModel;
+using JetBrains.Annotations;
+using JsonApiDotNetCore;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Queries.Expressions;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using Microsoft.AspNetCore.Http;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
+
+[UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
+public sealed class WheelSortDefinition : JsonApiResourceDefinition<Wheel, long>
+{
+    private readonly IHttpContextAccessor _httpContextAccessor;
+
+    public WheelSortDefinition(IResourceGraph resourceGraph, IHttpContextAccessor httpContextAccessor)
+        : base(resourceGraph)
+    {
+        ArgumentGuard.NotNull(httpContextAccessor, nameof(httpContextAccessor));
+
+        _httpContextAccessor = httpContextAccessor;
+    }
+
+    public override SortExpression? OnApplySort(SortExpression? existingSort)
+    {
+        if (_httpContextAccessor.HttpContext!.Request.Query["autoSort"] == "expr")
+        {
+            return CreateSortFromExpressionSyntax();
+        }
+
+        if (_httpContextAccessor.HttpContext!.Request.Query["autoSort"] == "lambda")
+        {
+            return CreateSortFromLambdaSyntax();
+        }
+
+        return existingSort;
+    }
+
+    private SortExpression CreateSortFromExpressionSyntax()
+    {
+        AttrAttribute paintColorAttribute = ResourceGraph.GetResourceType<ChromeWheel>().GetAttributeByPropertyName(nameof(ChromeWheel.PaintColor));
+        AttrAttribute hasTubeAttribute = ResourceGraph.GetResourceType<CarbonWheel>().GetAttributeByPropertyName(nameof(CarbonWheel.HasTube));
+
+        var cylinderCountChain = new ResourceFieldChainExpression(ImmutableArray.Create<ResourceFieldAttribute>(
+            ResourceGraph.GetResourceType<Wheel>().GetRelationshipByPropertyName(nameof(Wheel.Vehicle)),
+            ResourceGraph.GetResourceType<Car>().GetRelationshipByPropertyName(nameof(Car.Engine)),
+            ResourceGraph.GetResourceType<GasolineEngine>().GetRelationshipByPropertyName(nameof(GasolineEngine.Cylinders))));
+
+        return new SortExpression(new[]
+        {
+            new SortElementExpression(new ResourceFieldChainExpression(paintColorAttribute), true),
+            new SortElementExpression(new ResourceFieldChainExpression(hasTubeAttribute), false),
+            new SortElementExpression(new CountExpression(cylinderCountChain), true)
+        }.ToImmutableArray());
+    }
+
+    private SortExpression CreateSortFromLambdaSyntax()
+    {
+        return CreateSortExpressionFromLambda(new PropertySortOrder
+        {
+            (wheel => (wheel as ChromeWheel)!.PaintColor, ListSortDirection.Ascending),
+            (wheel => ((CarbonWheel)wheel).HasTube, ListSortDirection.Descending),
+            (wheel => ((GasolineEngine)((Car)wheel.Vehicle!).Engine).Cylinders.Count, ListSortDirection.Ascending)
+        });
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SortParseTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SortParseTests.cs
index 8b193aa390..3fcfe4433e 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SortParseTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/QueryStringParameters/SortParseTests.cs
@@ -72,6 +72,12 @@ public void Reader_Is_Enabled(JsonApiQueryStringParameters parametersDisabled, b
     [InlineData("sort[posts]", "caption,", "-, count function or field name expected.")]
     [InlineData("sort[posts]", "caption:", ", expected.")]
     [InlineData("sort[posts]", "caption,-", "Count function or field name expected.")]
+    [InlineData("sort[posts.contributors]", "some", "Attribute 'some' does not exist on resource type 'humans' or any of its derived types.")]
+    [InlineData("sort[posts.contributors]", "wife.father.some", "Attribute 'some' in 'wife.father.some' does not exist on resource type 'men'.")]
+    [InlineData("sort[posts.contributors]", "count(some)", "Relationship 'some' does not exist on resource type 'humans' or any of its derived types.")]
+    [InlineData("sort[posts.contributors]", "count(wife.some)", "Relationship 'some' in 'wife.some' does not exist on resource type 'women'.")]
+    [InlineData("sort[posts.contributors]", "age", "Attribute 'age' is defined on multiple derived types.")]
+    [InlineData("sort[posts.contributors]", "count(friends)", "Relationship 'friends' is defined on multiple derived types.")]
     public void Reader_Read_Fails(string parameterName, string parameterValue, string errorMessage)
     {
         // Act
@@ -103,6 +109,11 @@ public void Reader_Read_Fails(string parameterName, string parameterValue, strin
     [InlineData("sort[posts.labels]", "id,name", "posts.labels", "id,name")]
     [InlineData("sort[posts.comments]", "-createdAt,author.displayName,author.preferences.useDarkTheme", "posts.comments",
         "-createdAt,author.displayName,author.preferences.useDarkTheme")]
+    [InlineData("sort[posts.contributors]", "name,-maidenName,hasBeard", "posts.contributors", "name,-maidenName,hasBeard")]
+    [InlineData("sort[posts.contributors]", "husband.hasBeard,wife.maidenName", "posts.contributors", "husband.hasBeard,wife.maidenName")]
+    [InlineData("sort[posts.contributors]", "count(wife.husband.drinkingBuddies)", "posts.contributors", "count(wife.husband.drinkingBuddies)")]
+    [InlineData("sort[posts.contributors]", "wife.age", "posts.contributors", "wife.age")]
+    [InlineData("sort[posts.contributors]", "count(father.friends)", "posts.contributors", "count(father.friends)")]
     public void Reader_Read_Succeeds(string parameterName, string parameterValue, string scopeExpected, string valueExpected)
     {
         // Act
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs
new file mode 100644
index 0000000000..4152e9ed96
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs
@@ -0,0 +1,428 @@
+using System.ComponentModel;
+using System.Net;
+using FluentAssertions;
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.Queries.Expressions;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+using Microsoft.Extensions.Logging.Abstractions;
+using TestBuildingBlocks;
+using Xunit;
+
+namespace JsonApiDotNetCoreTests.UnitTests.ResourceDefinitions;
+
+public sealed class CreateSortExpressionFromLambdaTests
+{
+    [Fact]
+    public void Can_convert_chain_of_ToOne_relationships_ending_in_attribute()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileEntry, long>(resourceGraph);
+
+        // Act
+        SortExpression expression = resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileEntry, long>.PropertySortOrder
+        {
+            (file => file.Content, ListSortDirection.Descending),
+            (file => file.Name, ListSortDirection.Ascending),
+            (file => file.Length, ListSortDirection.Ascending),
+            (file => file.Parent.Name, ListSortDirection.Ascending),
+            (file => file.Parent.Parent.Name, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        string[] expected =
+        {
+            "-fileEntries:content",
+            "fileSystemEntries:name",
+            "fileEntries:length",
+            "fileSystemEntries:parent.fileSystemEntries:name",
+            "fileSystemEntries:parent.fileSystemEntries:parent.fileSystemEntries:name"
+        };
+
+        expression.ToFullString().Should().Be(string.Join(',', expected));
+    }
+
+    [Fact]
+    public void Can_convert_chain_of_ToOne_relationships_ending_in_count_of_ToMany_relationship()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<DirectoryEntry, long>(resourceGraph);
+
+        // Act
+        SortExpression expression = resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<DirectoryEntry, long>.PropertySortOrder
+        {
+            (directory => directory.Subdirectories.Count, ListSortDirection.Ascending),
+            // ReSharper disable once UseCollectionCountProperty
+            (directory => directory.Files.Count(), ListSortDirection.Descending),
+            (directory => directory.Children.Count, ListSortDirection.Ascending),
+            (directory => directory.Parent.Children.Count, ListSortDirection.Ascending),
+            (directory => directory.Parent.Parent.Children.Count, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        string[] expected =
+        {
+            "count(directoryEntries:subdirectories)",
+            "-count(directoryEntries:files)",
+            "count(fileSystemEntries:children)",
+            "count(fileSystemEntries:parent.fileSystemEntries:children)",
+            "count(fileSystemEntries:parent.fileSystemEntries:parent.fileSystemEntries:children)"
+        };
+
+        expression.ToFullString().Should().Be(string.Join(',', expected));
+    }
+
+    [Fact]
+    public void Can_convert_chain_with_conversion_to_derived_types()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileSystemEntry, long>(resourceGraph);
+
+        // Act
+        SortExpression expression = resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileSystemEntry, long>.PropertySortOrder
+        {
+            (entry => ((FileEntry)entry).Content, ListSortDirection.Ascending),
+            (entry => (entry.Parent as FileEntry)!.Content, ListSortDirection.Ascending),
+            (entry => ((DirectoryEntry)entry).Subdirectories.Count, ListSortDirection.Ascending),
+            (entry => ((DirectoryEntry)((FileEntry)entry).Parent).Files.Count, ListSortDirection.Ascending),
+            (entry => ((DirectoryEntry)(FileSystemEntry)(FileEntry)entry).Name, ListSortDirection.Descending)
+        });
+
+        // Assert
+        string[] expected =
+        {
+            "fileEntries:content",
+            "fileSystemEntries:parent.fileEntries:content",
+            "count(directoryEntries:subdirectories)",
+            "count(fileSystemEntries:parent.directoryEntries:files)",
+            "-fileSystemEntries:name"
+        };
+
+        expression.ToFullString().Should().Be(string.Join(',', expected));
+    }
+
+    [Fact]
+    public void Cannot_convert_unexposed_attribute()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileEntry, long>.PropertySortOrder
+        {
+            (file => file.IsCompressed, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().StartWith("The lambda expression 'file => Convert(file.IsCompressed, Object)' is invalid. ");
+        exception.Errors[0].Detail.Should().EndWith("Expected property for JSON:API attribute, but found 'file.IsCompressed'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_unexposed_ToMany_relationship()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileEntry, long>.PropertySortOrder
+        {
+            (file => file.Content.Length, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().StartWith("The lambda expression 'file => Convert(file.Content.Length, Object)' is invalid. ");
+        exception.Errors[0].Detail.Should().EndWith("Expected property for JSON:API to-many relationship, but found 'file.Content'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_unexposed_ToOne_relationship()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileEntry, long>.PropertySortOrder
+        {
+            (file => file.ParentDirectory!.Name, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().StartWith("The lambda expression 'file => file.ParentDirectory.Name' is invalid. ");
+        exception.Errors[0].Detail.Should().EndWith("Expected property for JSON:API to-one relationship, but found 'file.ParentDirectory'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_unexposed_resource_type()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = new ResourceGraphBuilder(new JsonApiOptions(), NullLoggerFactory.Instance).Add<FileSystemEntry, long>().Build();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileSystemEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileSystemEntry, long>.PropertySortOrder
+        {
+            (entry => ((FileEntry)entry).Content, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().StartWith("The lambda expression 'entry => Convert(entry, FileEntry).Content' is invalid. ");
+        exception.Errors[0].Detail.Should().EndWith("Resource of type 'FileEntry' does not exist.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_count_with_predicate()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<DirectoryEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<DirectoryEntry, long>.PropertySortOrder
+        {
+            (directory => directory.Files.Count(_ => true), ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().StartWith("The lambda expression 'directory => Convert(directory.Files.Count(_ => True), Object)' is invalid. ");
+        exception.Errors[0].Detail.Should().EndWith("Count method that takes a predicate is not supported.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_null_selector()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileSystemEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileSystemEntry, long>.PropertySortOrder
+        {
+            (_ => null, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().Be("The lambda expression '_ => null' is invalid. Unsupported expression body 'null'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_self_selector()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileSystemEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileSystemEntry, long>.PropertySortOrder
+        {
+            (entry => entry, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().Be("The lambda expression 'entry => entry' is invalid. Unsupported expression body 'entry'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_conditional_operator()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileEntry, long>.PropertySortOrder
+        {
+            (file => file.IsCompressed ? file.Content : file.Length, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().Match("The lambda expression '*' is invalid. Unsupported expression body '*'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_concatenation_operator()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileEntry, long>.PropertySortOrder
+        {
+            (file => file.Name + ":" + file.Content, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().Match("The lambda expression '*' is invalid. Unsupported expression body '*'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    [Fact]
+    public void Cannot_convert_projection_into_anonymous_type()
+    {
+        // Arrange
+        IResourceGraph resourceGraph = GetResourceGraph();
+
+        var resourceDefinition = new WrapperResourceDefinition<FileEntry, long>(resourceGraph);
+
+        // Act
+        Action action = () => resourceDefinition.GetSortExpressionFromLambda(new JsonApiResourceDefinition<FileEntry, long>.PropertySortOrder
+        {
+            (file => new
+            {
+                file.Length,
+                file.Content
+            }, ListSortDirection.Ascending)
+        });
+
+        // Assert
+        JsonApiException exception = action.Should().ThrowExactly<JsonApiException>().Which;
+
+        exception.Errors.ShouldHaveCount(1);
+        exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
+        exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
+        exception.Errors[0].Detail.Should().Match("The lambda expression '*' is invalid. Unsupported expression body '*'.");
+        exception.Errors[0].Source.Should().BeNull();
+    }
+
+    private static IResourceGraph GetResourceGraph()
+    {
+        var options = new JsonApiOptions();
+
+        // @formatter:wrap_chained_method_calls chop_always
+        // @formatter:keep_existing_linebreaks true
+
+        return new ResourceGraphBuilder(options, NullLoggerFactory.Instance)
+            .Add<FileSystemEntry, long>()
+            .Add<DirectoryEntry, long>()
+            .Add<FileEntry, long>()
+            .Build();
+
+        // @formatter:wrap_chained_method_calls restore
+        // @formatter:keep_existing_linebreaks restore
+    }
+
+    private sealed class WrapperResourceDefinition<TResource, TId> : JsonApiResourceDefinition<TResource, TId>
+        where TResource : class, IIdentifiable<TId>
+    {
+        public WrapperResourceDefinition(IResourceGraph resourceGraph)
+            : base(resourceGraph)
+        {
+        }
+
+        public SortExpression GetSortExpressionFromLambda(PropertySortOrder sortOrder)
+        {
+            return CreateSortExpressionFromLambda(sortOrder);
+        }
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    private abstract class FileSystemEntry : Identifiable<long>
+    {
+        [Attr]
+        public string Name { get; set; } = null!;
+
+        [HasOne]
+        public FileSystemEntry Parent { get; set; } = null!;
+
+        [HasMany]
+        public IList<FileSystemEntry> Children { get; set; } = new List<FileSystemEntry>();
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    private sealed class DirectoryEntry : FileSystemEntry
+    {
+        [HasMany]
+        public IList<DirectoryEntry> Subdirectories { get; set; } = new List<DirectoryEntry>();
+
+        [HasMany]
+        public IList<FileEntry> Files { get; set; } = new List<FileEntry>();
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    private sealed class FileEntry : FileSystemEntry
+    {
+        [Attr]
+        public string Content { get; set; } = null!;
+
+        [Attr]
+        public ulong Length { get; set; }
+
+        public bool IsCompressed { get; set; }
+
+        public DirectoryEntry? ParentDirectory { get; set; }
+    }
+}

From cb1f020764d8f6691302afc7d3342f7b3af05b6f Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Wed, 23 Mar 2022 14:50:48 +0100
Subject: [PATCH 09/19] Added missing tests for GET abstract/concrete base
 primary types at secondary/relationship endpoints

---
 .../ResourceInheritanceTests.cs               | 478 ++++++++++++++++--
 1 file changed, 439 insertions(+), 39 deletions(-)

diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
index c6753bf26e..05164f823b 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
@@ -384,7 +384,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
     }
 
     [Fact]
-    public async Task Cannot_get_secondary_resource_defined_in_derived_type_at_abstract_endpoint()
+    public async Task Can_get_secondary_resource_at_abstract_base_endpoint()
     {
         // Arrange
         Car car = _fakers.Car.Generate();
@@ -396,21 +396,77 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
             await dbContext.SaveChangesAsync();
         });
 
-        string route = $"/vehicles/{car.StringId}/engine";
+        string route = $"/motorVehicles/{car.StringId}/engine";
 
         // Act
         (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
 
         // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
 
-        responseDocument.Errors.ShouldHaveCount(1);
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
 
-        ErrorObject error = responseDocument.Errors[0];
-        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
-        error.Title.Should().Be("The requested relationship does not exist.");
-        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'engine'.");
-        error.Source.Should().BeNull();
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("gasolineEngines");
+        responseDocument.Data.SingleValue.Id.Should().Be(car.Engine.StringId);
+
+        responseDocument.Data.SingleValue.Links.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Links.Self.Should().Be($"/gasolineEngines/{car.Engine.StringId}");
+
+        responseDocument.Data.SingleValue.Attributes.ShouldHaveCount(4);
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("isHydrocarbonBased").With(value => value.Should().Be(car.Engine.IsHydrocarbonBased));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("capacity").With(value => value.Should().Be(car.Engine.Capacity));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("serialCode").With(value => value.Should().Be(((GasolineEngine)car.Engine).SerialCode));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("volatility").With(value => value.Should().Be(((GasolineEngine)car.Engine).Volatility));
+
+        responseDocument.Data.SingleValue.Relationships.ShouldHaveCount(1);
+
+        responseDocument.Data.SingleValue.Relationships.ShouldContainKey("cylinders").With(value =>
+        {
+            value.ShouldNotBeNull();
+            value.Links.ShouldNotBeNull();
+            value.Links.Self.Should().Be($"/gasolineEngines/{car.Engine.StringId}/relationships/cylinders");
+            value.Links.Related.Should().Be($"/gasolineEngines/{car.Engine.StringId}/cylinders");
+        });
+    }
+
+    [Fact]
+    public async Task Can_get_secondary_resource_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.CargoBox = _fakers.Box.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}/cargoBox";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("boxes");
+        responseDocument.Data.SingleValue.Id.Should().Be(tandem.CargoBox.StringId);
+
+        responseDocument.Data.SingleValue.Links.Should().BeNull();
+
+        responseDocument.Data.SingleValue.Attributes.ShouldHaveCount(3);
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("width").With(value => value.Should().Be(tandem.CargoBox.Width));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("height").With(value => value.Should().Be(tandem.CargoBox.Height));
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("depth").With(value => value.Should().Be(tandem.CargoBox.Depth));
+
+        responseDocument.Data.SingleValue.Relationships.Should().BeNull();
     }
 
     [Fact]
@@ -462,20 +518,19 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
     }
 
     [Fact]
-    public async Task Cannot_get_secondary_resources_defined_in_derived_type_at_abstract_endpoint()
+    public async Task Cannot_get_secondary_resource_defined_in_derived_type_at_abstract_endpoint()
     {
         // Arrange
-        Truck truck = _fakers.Truck.Generate();
-        truck.Engine = _fakers.DieselEngine.Generate();
-        truck.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
 
         await _testContext.RunOnDatabaseAsync(async dbContext =>
         {
-            dbContext.Vehicles.Add(truck);
+            dbContext.Vehicles.Add(car);
             await dbContext.SaveChangesAsync();
         });
 
-        string route = $"/vehicles/{truck.StringId}/features";
+        string route = $"/vehicles/{car.StringId}/engine";
 
         // Act
         (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
@@ -488,12 +543,12 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.NotFound);
         error.Title.Should().Be("The requested relationship does not exist.");
-        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'features'.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'engine'.");
         error.Source.Should().BeNull();
     }
 
     [Fact]
-    public async Task Cannot_get_secondary_resources_defined_in_derived_type_at_concrete_base_endpoint()
+    public async Task Cannot_get_secondary_resource_defined_in_derived_type_at_concrete_base_endpoint()
     {
         // Arrange
         Tandem tandem = _fakers.Tandem.Generate();
@@ -523,7 +578,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
     }
 
     [Fact]
-    public async Task Can_get_secondary_resources_at_concrete_derived_endpoint()
+    public async Task Can_get_secondary_resources_at_abstract_base_endpoint()
     {
         // Arrange
         Car car = _fakers.Car.Generate();
@@ -536,7 +591,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
             await dbContext.SaveChangesAsync();
         });
 
-        string route = $"/cars/{car.StringId}/wheels";
+        string route = $"/vehicles/{car.StringId}/wheels";
 
         // Act
         (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
@@ -589,11 +644,84 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
     }
 
     [Fact]
-    public async Task Cannot_get_ToOne_relationship_defined_in_derived_type_at_abstract_endpoint()
+    public async Task Can_get_secondary_resources_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().Concat(_fakers.CarbonWheel.Generate(2)).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == tandem.Wheels.ElementAt(0).StringId);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == tandem.Wheels.ElementAt(1).StringId);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == tandem.Wheels.ElementAt(2).StringId);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == tandem.Wheels.ElementAt(3).StringId);
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue.Where(value => value.Type == "chromeWheels"))
+        {
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/chromeWheels/{resource.Id}");
+
+            resource.Attributes.ShouldHaveCount(2);
+            resource.Attributes.ShouldContainKey("radius");
+            resource.Attributes.ShouldContainKey("paintColor");
+        }
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue.Where(value => value.Type == "carbonWheels"))
+        {
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/carbonWheels/{resource.Id}");
+
+            resource.Attributes.ShouldHaveCount(2);
+            resource.Attributes.ShouldContainKey("radius");
+            resource.Attributes.ShouldContainKey("hasTube");
+        }
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue)
+        {
+            resource.Relationships.ShouldHaveCount(1);
+
+            resource.Relationships.ShouldContainKey("vehicle").With(value =>
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/{resource.Type}/{resource.Id}/relationships/vehicle");
+                value.Links.Related.Should().Be($"/{resource.Type}/{resource.Id}/vehicle");
+            });
+        }
+    }
+
+    [Fact]
+    public async Task Can_get_secondary_resources_at_concrete_derived_endpoint()
     {
         // Arrange
         Car car = _fakers.Car.Generate();
         car.Engine = _fakers.GasolineEngine.Generate();
+        car.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().Concat(_fakers.CarbonWheel.Generate(2)).ToHashSet();
 
         await _testContext.RunOnDatabaseAsync(async dbContext =>
         {
@@ -601,7 +729,73 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
             await dbContext.SaveChangesAsync();
         });
 
-        string route = $"/vehicles/{car.StringId}/relationships/engine";
+        string route = $"/cars/{car.StringId}/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(0).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(1).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(2).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(3).StringId);
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue.Where(value => value.Type == "chromeWheels"))
+        {
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/chromeWheels/{resource.Id}");
+
+            resource.Attributes.ShouldHaveCount(2);
+            resource.Attributes.ShouldContainKey("radius");
+            resource.Attributes.ShouldContainKey("paintColor");
+        }
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue.Where(value => value.Type == "carbonWheels"))
+        {
+            resource.Links.ShouldNotBeNull();
+            resource.Links.Self.Should().Be($"/carbonWheels/{resource.Id}");
+
+            resource.Attributes.ShouldHaveCount(2);
+            resource.Attributes.ShouldContainKey("radius");
+            resource.Attributes.ShouldContainKey("hasTube");
+        }
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue)
+        {
+            resource.Relationships.ShouldHaveCount(1);
+
+            resource.Relationships.ShouldContainKey("vehicle").With(value =>
+            {
+                value.ShouldNotBeNull();
+                value.Links.ShouldNotBeNull();
+                value.Links.Self.Should().Be($"/{resource.Type}/{resource.Id}/relationships/vehicle");
+                value.Links.Related.Should().Be($"/{resource.Type}/{resource.Id}/vehicle");
+            });
+        }
+    }
+
+    [Fact]
+    public async Task Cannot_get_secondary_resources_defined_in_derived_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+        truck.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{truck.StringId}/features";
 
         // Act
         (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
@@ -614,10 +808,102 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.NotFound);
         error.Title.Should().Be("The requested relationship does not exist.");
-        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'engine'.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'features'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_get_secondary_resources_defined_in_derived_type_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}/features";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'bikes' does not contain a relationship named 'features'.");
         error.Source.Should().BeNull();
     }
 
+    [Fact]
+    public async Task Can_get_ToOne_relationship_at_abstract_base_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/motorVehicles/{car.StringId}/relationships/engine";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+        responseDocument.Links.Related.Should().Be($"/motorVehicles/{car.StringId}/engine");
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("gasolineEngines");
+        responseDocument.Data.SingleValue.Id.Should().Be(car.Engine.StringId);
+        responseDocument.Data.SingleValue.Links.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_get_ToOne_relationship_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.CargoBox = _fakers.Box.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}/relationships/cargoBox";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+        responseDocument.Links.Related.Should().Be($"/bikes/{tandem.StringId}/cargoBox");
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("boxes");
+        responseDocument.Data.SingleValue.Id.Should().Be(tandem.CargoBox.StringId);
+        responseDocument.Data.SingleValue.Links.Should().BeNull();
+    }
+
     [Fact]
     public async Task Can_get_ToOne_relationship_at_concrete_derived_endpoint()
     {
@@ -650,20 +936,19 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
     }
 
     [Fact]
-    public async Task Cannot_get_ToMany_relationship_defined_in_derived_type_at_abstract_endpoint()
+    public async Task Cannot_get_ToOne_relationship_defined_in_derived_type_at_abstract_endpoint()
     {
         // Arrange
-        Truck truck = _fakers.Truck.Generate();
-        truck.Engine = _fakers.DieselEngine.Generate();
-        truck.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
 
         await _testContext.RunOnDatabaseAsync(async dbContext =>
         {
-            dbContext.Vehicles.Add(truck);
+            dbContext.Vehicles.Add(car);
             await dbContext.SaveChangesAsync();
         });
 
-        string route = $"/vehicles/{truck.StringId}/relationships/features";
+        string route = $"/vehicles/{car.StringId}/relationships/engine";
 
         // Act
         (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
@@ -676,16 +961,55 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.NotFound);
         error.Title.Should().Be("The requested relationship does not exist.");
-        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'features'.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'engine'.");
         error.Source.Should().BeNull();
     }
 
     [Fact]
-    public async Task Cannot_get_ToMany_relationship_defined_in_derived_type_at_concrete_base_endpoint()
+    public async Task Can_get_ToMany_relationship_at_abstract_base_endpoint()
+    {
+        // Arrange
+        Car car = _fakers.Car.Generate();
+        car.Engine = _fakers.GasolineEngine.Generate();
+        car.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().Concat(_fakers.CarbonWheel.Generate(2)).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(car);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{car.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+        responseDocument.Links.Related.Should().Be($"/vehicles/{car.StringId}/wheels");
+
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(0).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == car.Wheels.ElementAt(1).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(2).StringId);
+        responseDocument.Data.ManyValue.Should().ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == car.Wheels.ElementAt(3).StringId);
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue)
+        {
+            resource.Links.Should().BeNull();
+        }
+    }
+
+    [Fact]
+    public async Task Can_get_ToMany_relationship_at_concrete_base_endpoint()
     {
         // Arrange
         Tandem tandem = _fakers.Tandem.Generate();
-        tandem.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+        tandem.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().Concat(_fakers.CarbonWheel.Generate(2)).ToHashSet();
 
         await _testContext.RunOnDatabaseAsync(async dbContext =>
         {
@@ -693,21 +1017,36 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
             await dbContext.SaveChangesAsync();
         });
 
-        string route = $"/bikes/{tandem.StringId}/relationships/features";
+        string route = $"/bikes/{tandem.StringId}/relationships/wheels";
 
         // Act
         (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
 
         // Assert
-        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
 
-        responseDocument.Errors.ShouldHaveCount(1);
+        responseDocument.Links.ShouldNotBeNull();
+        responseDocument.Links.Self.Should().Be(route);
+        responseDocument.Links.Related.Should().Be($"/bikes/{tandem.StringId}/wheels");
 
-        ErrorObject error = responseDocument.Errors[0];
-        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
-        error.Title.Should().Be("The requested relationship does not exist.");
-        error.Detail.Should().Be("Resource of type 'bikes' does not contain a relationship named 'features'.");
-        error.Source.Should().BeNull();
+        responseDocument.Data.ManyValue.ShouldHaveCount(4);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == tandem.Wheels.ElementAt(0).StringId);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "chromeWheels" && resource.Id == tandem.Wheels.ElementAt(1).StringId);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == tandem.Wheels.ElementAt(2).StringId);
+
+        responseDocument.Data.ManyValue.Should()
+            .ContainSingle(resource => resource.Type == "carbonWheels" && resource.Id == tandem.Wheels.ElementAt(3).StringId);
+
+        foreach (ResourceObject resource in responseDocument.Data.ManyValue)
+        {
+            resource.Links.Should().BeNull();
+        }
     }
 
     [Fact]
@@ -749,6 +1088,67 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         }
     }
 
+    [Fact]
+    public async Task Cannot_get_ToMany_relationship_defined_in_derived_type_at_abstract_endpoint()
+    {
+        // Arrange
+        Truck truck = _fakers.Truck.Generate();
+        truck.Engine = _fakers.DieselEngine.Generate();
+        truck.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(truck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{truck.StringId}/relationships/features";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'vehicles' does not contain a relationship named 'features'.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_get_ToMany_relationship_defined_in_derived_type_at_concrete_base_endpoint()
+    {
+        // Arrange
+        Tandem tandem = _fakers.Tandem.Generate();
+        tandem.Features = _fakers.GenericFeature.Generate(1).ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(tandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/bikes/{tandem.StringId}/relationships/features";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteGetAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested relationship does not exist.");
+        error.Detail.Should().Be("Resource of type 'bikes' does not contain a relationship named 'features'.");
+        error.Source.Should().BeNull();
+    }
+
     [Fact]
     public async Task Can_get_primary_resources_at_abstract_endpoint_with_all_sparse_fieldsets()
     {

From ad8c4c8191144fd5c5e8ce7f7fbabea3ba5cc36a Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Thu, 24 Mar 2022 13:42:08 +0100
Subject: [PATCH 10/19] Resource graph validation: fail if field from base type
 does not exist on derived type

---
 .../Configuration/ResourceGraph.cs            |  4 +-
 .../Configuration/ResourceGraphBuilder.cs     | 37 ++++++++
 .../ServiceCollectionExtensions.cs            |  2 +-
 .../CreateSortExpressionFromLambdaTests.cs    |  2 +-
 .../ResourceGraphBuilderTests.cs              | 88 +++++++++++++++++++
 .../ServiceCollectionExtensionsTests.cs       |  3 +-
 6 files changed, 131 insertions(+), 5 deletions(-)

diff --git a/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs b/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs
index 6815fbf076..d693fa2c3c 100644
--- a/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs
+++ b/src/JsonApiDotNetCore/Configuration/ResourceGraph.cs
@@ -42,7 +42,7 @@ public ResourceType GetResourceType(string publicName)
 
         if (resourceType == null)
         {
-            throw new InvalidOperationException($"Resource type '{publicName}' does not exist.");
+            throw new InvalidOperationException($"Resource type '{publicName}' does not exist in the resource graph.");
         }
 
         return resourceType;
@@ -63,7 +63,7 @@ public ResourceType GetResourceType(Type resourceClrType)
 
         if (resourceType == null)
         {
-            throw new InvalidOperationException($"Resource of type '{resourceClrType.Name}' does not exist.");
+            throw new InvalidOperationException($"Type '{resourceClrType}' does not exist in the resource graph.");
         }
 
         return resourceType;
diff --git a/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs b/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
index 397226ff43..428b14d32e 100644
--- a/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
+++ b/src/JsonApiDotNetCore/Configuration/ResourceGraphBuilder.cs
@@ -46,6 +46,7 @@ public IResourceGraph Build()
         SetFieldTypes(resourceGraph);
         SetRelationshipTypes(resourceGraph);
         SetDirectlyDerivedTypes(resourceGraph);
+        ValidateFieldsInDerivedTypes(resourceGraph);
 
         return resourceGraph;
     }
@@ -105,6 +106,42 @@ private static void SetDirectlyDerivedTypes(ResourceGraph resourceGraph)
         }
     }
 
+    private void ValidateFieldsInDerivedTypes(ResourceGraph resourceGraph)
+    {
+        foreach (ResourceType resourceType in resourceGraph.GetResourceTypes())
+        {
+            if (resourceType.BaseType != null)
+            {
+                ValidateAttributesInDerivedType(resourceType);
+                ValidateRelationshipsInDerivedType(resourceType);
+            }
+        }
+    }
+
+    private static void ValidateAttributesInDerivedType(ResourceType resourceType)
+    {
+        foreach (AttrAttribute attribute in resourceType.BaseType!.Attributes)
+        {
+            if (resourceType.FindAttributeByPublicName(attribute.PublicName) == null)
+            {
+                throw new InvalidConfigurationException($"Attribute '{attribute.PublicName}' from base type " +
+                    $"'{resourceType.BaseType.ClrType}' does not exist in derived type '{resourceType.ClrType}'.");
+            }
+        }
+    }
+
+    private static void ValidateRelationshipsInDerivedType(ResourceType resourceType)
+    {
+        foreach (RelationshipAttribute relationship in resourceType.BaseType!.Relationships)
+        {
+            if (resourceType.FindRelationshipByPublicName(relationship.PublicName) == null)
+            {
+                throw new InvalidConfigurationException($"Relationship '{relationship.PublicName}' from base type " +
+                    $"'{resourceType.BaseType.ClrType}' does not exist in derived type '{resourceType.ClrType}'.");
+            }
+        }
+    }
+
     public ResourceGraphBuilder Add(DbContext dbContext)
     {
         ArgumentGuard.NotNull(dbContext, nameof(dbContext));
diff --git a/src/JsonApiDotNetCore/Configuration/ServiceCollectionExtensions.cs b/src/JsonApiDotNetCore/Configuration/ServiceCollectionExtensions.cs
index 64a15e2eda..64a99021d4 100644
--- a/src/JsonApiDotNetCore/Configuration/ServiceCollectionExtensions.cs
+++ b/src/JsonApiDotNetCore/Configuration/ServiceCollectionExtensions.cs
@@ -111,7 +111,7 @@ private static void RegisterTypeForUnboundInterfaces(IServiceCollection serviceC
 
         if (!seenCompatibleInterface)
         {
-            throw new InvalidConfigurationException($"{implementationType} does not implement any of the expected JsonApiDotNetCore interfaces.");
+            throw new InvalidConfigurationException($"Type '{implementationType}' does not implement any of the expected JsonApiDotNetCore interfaces.");
         }
     }
 
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs
index 4152e9ed96..aff961eeeb 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/ResourceDefinitions/CreateSortExpressionFromLambdaTests.cs
@@ -205,7 +205,7 @@ public void Cannot_convert_unexposed_resource_type()
         exception.Errors[0].StatusCode.Should().Be(HttpStatusCode.InternalServerError);
         exception.Errors[0].Title.Should().StartWith("Invalid lambda expression for sorting from resource definition. It should ");
         exception.Errors[0].Detail.Should().StartWith("The lambda expression 'entry => Convert(entry, FileEntry).Content' is invalid. ");
-        exception.Errors[0].Detail.Should().EndWith("Resource of type 'FileEntry' does not exist.");
+        exception.Errors[0].Detail.Should().EndWith($"Type '{typeof(FileEntry)}' does not exist in the resource graph.");
         exception.Errors[0].Source.Should().BeNull();
     }
 
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/ResourceGraph/ResourceGraphBuilderTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/ResourceGraph/ResourceGraphBuilderTests.cs
index 6b762fb2ef..3fc221c190 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/ResourceGraph/ResourceGraphBuilderTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/ResourceGraph/ResourceGraphBuilderTests.cs
@@ -197,6 +197,60 @@ public void Cannot_build_graph_with_missing_related_HasMany_resource()
             $"depends on '{typeof(ResourceWithAttribute)}', which was not added to the resource graph.");
     }
 
+    [Fact]
+    public void Cannot_build_graph_with_different_attribute_name_in_derived_type()
+    {
+        // Arrange
+        var options = new JsonApiOptions();
+        var builder = new ResourceGraphBuilder(options, NullLoggerFactory.Instance);
+
+        builder.Add<AbstractBaseResource, int>();
+        builder.Add<DerivedAlternateAttributeName, int>();
+
+        // Act
+        Action action = () => builder.Build();
+
+        // Assert
+        action.Should().ThrowExactly<InvalidConfigurationException>().WithMessage("Attribute 'baseValue' from base type " +
+            $"'{typeof(AbstractBaseResource)}' does not exist in derived type '{typeof(DerivedAlternateAttributeName)}'.");
+    }
+
+    [Fact]
+    public void Cannot_build_graph_with_different_ToOne_relationship_name_in_derived_type()
+    {
+        // Arrange
+        var options = new JsonApiOptions();
+        var builder = new ResourceGraphBuilder(options, NullLoggerFactory.Instance);
+
+        builder.Add<AbstractBaseResource, int>();
+        builder.Add<DerivedAlternateToOneRelationshipName, int>();
+
+        // Act
+        Action action = () => builder.Build();
+
+        // Assert
+        action.Should().ThrowExactly<InvalidConfigurationException>().WithMessage("Relationship 'baseToOne' from base type " +
+            $"'{typeof(AbstractBaseResource)}' does not exist in derived type '{typeof(DerivedAlternateToOneRelationshipName)}'.");
+    }
+
+    [Fact]
+    public void Cannot_build_graph_with_different_ToMany_relationship_name_in_derived_type()
+    {
+        // Arrange
+        var options = new JsonApiOptions();
+        var builder = new ResourceGraphBuilder(options, NullLoggerFactory.Instance);
+
+        builder.Add<AbstractBaseResource, int>();
+        builder.Add<DerivedAlternateToManyRelationshipName, int>();
+
+        // Act
+        Action action = () => builder.Build();
+
+        // Assert
+        action.Should().ThrowExactly<InvalidConfigurationException>().WithMessage("Relationship 'baseToMany' from base type " +
+            $"'{typeof(AbstractBaseResource)}' does not exist in derived type '{typeof(DerivedAlternateToManyRelationshipName)}'.");
+    }
+
     [Fact]
     public void Logs_warning_when_adding_non_resource_type()
     {
@@ -405,4 +459,38 @@ public sealed class ResourceWithIdOverride : Identifiable<long>
         [Attr(Capabilities = AttrCapabilities.AllowFilter)]
         public override long Id { get; set; }
     }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    public abstract class AbstractBaseResource : Identifiable<int>
+    {
+        [Attr(PublicName = "baseValue")]
+        public virtual int Value { get; set; }
+
+        [HasOne(PublicName = "baseToOne")]
+        public virtual AbstractBaseResource? BaseToOne { get; set; }
+
+        [HasMany(PublicName = "baseToMany")]
+        public virtual ISet<AbstractBaseResource> BaseToMany { get; set; } = new HashSet<AbstractBaseResource>();
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    public sealed class DerivedAlternateAttributeName : AbstractBaseResource
+    {
+        [Attr(PublicName = "derivedValue")]
+        public override int Value { get; set; }
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    public sealed class DerivedAlternateToOneRelationshipName : AbstractBaseResource
+    {
+        [HasOne(PublicName = "derivedToOne")]
+        public override AbstractBaseResource? BaseToOne { get; set; }
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    public sealed class DerivedAlternateToManyRelationshipName : AbstractBaseResource
+    {
+        [HasMany(PublicName = "derivedToMany")]
+        public override ISet<AbstractBaseResource> BaseToMany { get; set; } = new HashSet<AbstractBaseResource>();
+    }
 }
diff --git a/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs b/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs
index c1e2e6efcf..3213adcbe6 100644
--- a/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs
+++ b/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs
@@ -95,7 +95,8 @@ public void AddResourceService_Throws_If_Type_Does_Not_Implement_Any_Interfaces(
         Action action = () => services.AddResourceService<int>();
 
         // Assert
-        action.Should().ThrowExactly<InvalidConfigurationException>();
+        action.Should().ThrowExactly<InvalidConfigurationException>()
+            .WithMessage("Type 'System.Int32' does not implement any of the expected JsonApiDotNetCore interfaces.");
     }
 
     [Fact]

From 33e31838bf57cacf1bf62ba6b5bdba0b2a7eee14 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Fri, 25 Mar 2022 00:00:24 +0100
Subject: [PATCH 11/19] Clarified error message on type mismatch in request
 body

---
 .../Serialization/Request/Adapters/ResourceIdentityAdapter.cs | 4 ++--
 .../AtomicCreateResourceWithToManyRelationshipTests.cs        | 2 +-
 .../AtomicCreateResourceWithToOneRelationshipTests.cs         | 2 +-
 .../Relationships/AtomicAddToToManyRelationshipTests.cs       | 2 +-
 .../Relationships/AtomicRemoveFromToManyRelationshipTests.cs  | 2 +-
 .../Relationships/AtomicReplaceToManyRelationshipTests.cs     | 2 +-
 .../Relationships/AtomicUpdateToOneRelationshipTests.cs       | 2 +-
 .../Resources/AtomicReplaceToManyRelationshipTests.cs         | 2 +-
 .../Updating/Resources/AtomicUpdateResourceTests.cs           | 2 +-
 .../Updating/Resources/AtomicUpdateToOneRelationshipTests.cs  | 2 +-
 .../ReadWrite/Creating/CreateResourceTests.cs                 | 2 +-
 .../Creating/CreateResourceWithToManyRelationshipTests.cs     | 2 +-
 .../Creating/CreateResourceWithToOneRelationshipTests.cs      | 2 +-
 .../Updating/Relationships/AddToToManyRelationshipTests.cs    | 2 +-
 .../Relationships/RemoveFromToManyRelationshipTests.cs        | 2 +-
 .../Updating/Relationships/ReplaceToManyRelationshipTests.cs  | 2 +-
 .../Updating/Relationships/UpdateToOneRelationshipTests.cs    | 2 +-
 .../Updating/Resources/ReplaceToManyRelationshipTests.cs      | 2 +-
 .../ReadWrite/Updating/Resources/UpdateResourceTests.cs       | 2 +-
 .../Updating/Resources/UpdateToOneRelationshipTests.cs        | 2 +-
 20 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs b/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs
index f453b8dd21..62519cbc50 100644
--- a/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs
+++ b/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs
@@ -72,8 +72,8 @@ private static void AssertIsCompatibleResourceType(ResourceType actual, Resource
         if (expected != null && !expected.ClrType.IsAssignableFrom(actual.ClrType))
         {
             string message = relationshipName != null
-                ? $"Type '{actual.PublicName}' is incompatible with type '{expected.PublicName}' of relationship '{relationshipName}'."
-                : $"Type '{actual.PublicName}' is incompatible with type '{expected.PublicName}'.";
+                ? $"Type '{actual.PublicName}' is not convertible to type '{expected.PublicName}' of relationship '{relationshipName}'."
+                : $"Type '{actual.PublicName}' is not convertible to type '{expected.PublicName}'.";
 
             throw new ModelConversionException(state.Position, "Incompatible resource type found.", message, HttpStatusCode.Conflict);
         }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToManyRelationshipTests.cs
index 465f39cee1..32024c03dd 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToManyRelationshipTests.cs
@@ -464,7 +464,7 @@ public async Task Cannot_create_on_relationship_type_mismatch()
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'performers' of relationship 'performers'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'performers' of relationship 'performers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data/relationships/performers/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToOneRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToOneRelationshipTests.cs
index 64fc6e66d3..a0ed043ae8 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToOneRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Creating/AtomicCreateResourceWithToOneRelationshipTests.cs
@@ -648,7 +648,7 @@ public async Task Cannot_create_on_relationship_type_mismatch()
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'lyrics' of relationship 'lyric'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'lyrics' of relationship 'lyric'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data/relationships/lyric/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicAddToToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicAddToToManyRelationshipTests.cs
index bd97c23411..d249ec2563 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicAddToToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicAddToToManyRelationshipTests.cs
@@ -1026,7 +1026,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'performers' of relationship 'performers'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'performers' of relationship 'performers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicRemoveFromToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicRemoveFromToManyRelationshipTests.cs
index 1e6787a0d7..e15e926293 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicRemoveFromToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicRemoveFromToManyRelationshipTests.cs
@@ -986,7 +986,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'performers' of relationship 'performers'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'performers' of relationship 'performers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicReplaceToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicReplaceToManyRelationshipTests.cs
index ee3ea791a5..abb9b423d1 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicReplaceToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicReplaceToManyRelationshipTests.cs
@@ -1135,7 +1135,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'performers' of relationship 'performers'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'performers' of relationship 'performers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicUpdateToOneRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicUpdateToOneRelationshipTests.cs
index b66a5dfc26..13bc5a107f 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicUpdateToOneRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Relationships/AtomicUpdateToOneRelationshipTests.cs
@@ -1300,7 +1300,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'lyrics' of relationship 'lyric'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'lyrics' of relationship 'lyric'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicReplaceToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicReplaceToManyRelationshipTests.cs
index 98b8892800..8ea9ac6574 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicReplaceToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicReplaceToManyRelationshipTests.cs
@@ -794,7 +794,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'performers' of relationship 'performers'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'performers' of relationship 'performers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data/relationships/performers/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateResourceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateResourceTests.cs
index f8051e369c..1679ff3fa3 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateResourceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateResourceTests.cs
@@ -1149,7 +1149,7 @@ public async Task Cannot_update_on_resource_type_mismatch_between_ref_and_data()
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'performers'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'performers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateToOneRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateToOneRelationshipTests.cs
index efa3813d74..b2a7f04262 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateToOneRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Updating/Resources/AtomicUpdateToOneRelationshipTests.cs
@@ -1041,7 +1041,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'playlists' is incompatible with type 'lyrics' of relationship 'lyric'.");
+        error.Detail.Should().Be("Type 'playlists' is not convertible to type 'lyrics' of relationship 'lyric'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/atomic:operations[0]/data/relationships/lyric/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceTests.cs
index 168a8d0e90..f0250ae5f4 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceTests.cs
@@ -722,7 +722,7 @@ public async Task Cannot_create_on_resource_type_mismatch_between_url_and_body()
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'rgbColors' is incompatible with type 'workItems'.");
+        error.Detail.Should().Be("Type 'rgbColors' is not convertible to type 'workItems'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToManyRelationshipTests.cs
index b7075a346b..a73de969d6 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToManyRelationshipTests.cs
@@ -556,7 +556,7 @@ public async Task Cannot_create_on_relationship_type_mismatch()
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'rgbColors' is incompatible with type 'userAccounts' of relationship 'subscribers'.");
+        error.Detail.Should().Be("Type 'rgbColors' is not convertible to type 'userAccounts' of relationship 'subscribers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data/relationships/subscribers/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToOneRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToOneRelationshipTests.cs
index b70e53eaf0..b9357c9247 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToOneRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Creating/CreateResourceWithToOneRelationshipTests.cs
@@ -641,7 +641,7 @@ public async Task Cannot_create_on_relationship_type_mismatch()
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'rgbColors' is incompatible with type 'userAccounts' of relationship 'assignee'.");
+        error.Detail.Should().Be("Type 'rgbColors' is not convertible to type 'userAccounts' of relationship 'assignee'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data/relationships/assignee/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/AddToToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/AddToToManyRelationshipTests.cs
index f2ec5d10bd..9e65ef6114 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/AddToToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/AddToToManyRelationshipTests.cs
@@ -634,7 +634,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'userAccounts' is incompatible with type 'workTags' of relationship 'tags'.");
+        error.Detail.Should().Be("Type 'userAccounts' is not convertible to type 'workTags' of relationship 'tags'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/RemoveFromToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/RemoveFromToManyRelationshipTests.cs
index 8d0b99a062..7ee80fbdf6 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/RemoveFromToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/RemoveFromToManyRelationshipTests.cs
@@ -750,7 +750,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'userAccounts' is incompatible with type 'workTags' of relationship 'tags'.");
+        error.Detail.Should().Be("Type 'userAccounts' is not convertible to type 'workTags' of relationship 'tags'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/ReplaceToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/ReplaceToManyRelationshipTests.cs
index 84052132f9..ef7d0eacc9 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/ReplaceToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/ReplaceToManyRelationshipTests.cs
@@ -661,7 +661,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'userAccounts' is incompatible with type 'workTags' of relationship 'tags'.");
+        error.Detail.Should().Be("Type 'userAccounts' is not convertible to type 'workTags' of relationship 'tags'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/UpdateToOneRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/UpdateToOneRelationshipTests.cs
index c7174ec225..832a788d5d 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/UpdateToOneRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Relationships/UpdateToOneRelationshipTests.cs
@@ -689,7 +689,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'rgbColors' is incompatible with type 'userAccounts' of relationship 'assignee'.");
+        error.Detail.Should().Be("Type 'rgbColors' is not convertible to type 'userAccounts' of relationship 'assignee'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/ReplaceToManyRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/ReplaceToManyRelationshipTests.cs
index 0c44fb6995..7a7924cafa 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/ReplaceToManyRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/ReplaceToManyRelationshipTests.cs
@@ -697,7 +697,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'rgbColors' is incompatible with type 'userAccounts' of relationship 'subscribers'.");
+        error.Detail.Should().Be("Type 'rgbColors' is not convertible to type 'userAccounts' of relationship 'subscribers'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data/relationships/subscribers/data[0]/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateResourceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateResourceTests.cs
index 87ced913e3..41acec8acf 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateResourceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateResourceTests.cs
@@ -1039,7 +1039,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'rgbColors' is incompatible with type 'workItems'.");
+        error.Detail.Should().Be("Type 'rgbColors' is not convertible to type 'workItems'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateToOneRelationshipTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateToOneRelationshipTests.cs
index 1d0b689713..6861586f86 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateToOneRelationshipTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ReadWrite/Updating/Resources/UpdateToOneRelationshipTests.cs
@@ -836,7 +836,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
         ErrorObject error = responseDocument.Errors[0];
         error.StatusCode.Should().Be(HttpStatusCode.Conflict);
         error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
-        error.Detail.Should().Be("Type 'rgbColors' is incompatible with type 'userAccounts' of relationship 'assignee'.");
+        error.Detail.Should().Be("Type 'rgbColors' is not convertible to type 'userAccounts' of relationship 'assignee'.");
         error.Source.ShouldNotBeNull();
         error.Source.Pointer.Should().Be("/data/relationships/assignee/data/type");
         error.Meta.ShouldContainKey("requestBody").With(value => value.ShouldNotBeNull().ToString().ShouldNotBeEmpty());

From 3a2a3999ad0774fed90b508511b36f9961b4c481 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Thu, 24 Mar 2022 14:51:00 +0100
Subject: [PATCH 12/19] Rename inheritance tests

---
 .../ResourceInheritance/ResourceInheritanceFakers.cs          | 2 +-
 ...rceInheritanceTests.cs => ResourceInheritanceReadTests.cs} | 4 ++--
 ...ablePerHierarchyTests.cs => TablePerHierarchyReadTests.cs} | 4 ++--
 .../{TablePerTypeTests.cs => TablePerTypeReadTests.cs}        | 4 ++--
 4 files changed, 7 insertions(+), 7 deletions(-)
 rename test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/{ResourceInheritanceTests.cs => ResourceInheritanceReadTests.cs} (99%)
 rename test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/{TablePerHierarchyTests.cs => TablePerHierarchyReadTests.cs} (51%)
 rename test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/{TablePerTypeTests.cs => TablePerTypeReadTests.cs} (53%)

diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
index 3842978581..f0f74e5c1e 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
@@ -108,7 +108,7 @@ internal sealed class ResourceInheritanceFakers : FakerContainer
     private readonly Lazy<Faker<StringValue>> _lazyStringValueFaker = new(() =>
         new Faker<StringValue>()
             .UseSeed(GetFakerSeed())
-            .RuleFor(stringValue => stringValue.Content, faker => faker.Lorem.Text()));
+            .RuleFor(stringValue => stringValue.Content, faker => faker.Lorem.Lines(1)));
 
     private readonly Lazy<Faker<NumberProperty>> _lazyNumberPropertyFaker = new(() =>
         new Faker<NumberProperty>()
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceReadTests.cs
similarity index 99%
rename from test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
rename to test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceReadTests.cs
index 05164f823b..8bf9349a04 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceReadTests.cs
@@ -10,13 +10,13 @@
 
 namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
 
-public abstract class ResourceInheritanceTests<TDbContext> : IClassFixture<IntegrationTestContext<TestableStartup<TDbContext>, TDbContext>>
+public abstract class ResourceInheritanceReadTests<TDbContext> : IClassFixture<IntegrationTestContext<TestableStartup<TDbContext>, TDbContext>>
     where TDbContext : ResourceInheritanceDbContext
 {
     private readonly IntegrationTestContext<TestableStartup<TDbContext>, TDbContext> _testContext;
     private readonly ResourceInheritanceFakers _fakers = new();
 
-    protected ResourceInheritanceTests(IntegrationTestContext<TestableStartup<TDbContext>, TDbContext> testContext)
+    protected ResourceInheritanceReadTests(IntegrationTestContext<TestableStartup<TDbContext>, TDbContext> testContext)
     {
         _testContext = testContext;
 
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyReadTests.cs
similarity index 51%
rename from test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyTests.cs
rename to test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyReadTests.cs
index 5b6a68ad95..e9d3df4ac0 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyReadTests.cs
@@ -4,9 +4,9 @@
 namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerHierarchy;
 
 [UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
-public sealed class TablePerHierarchyTests : ResourceInheritanceTests<TablePerHierarchyDbContext>
+public sealed class TablePerHierarchyReadTests : ResourceInheritanceReadTests<TablePerHierarchyDbContext>
 {
-    public TablePerHierarchyTests(IntegrationTestContext<TestableStartup<TablePerHierarchyDbContext>, TablePerHierarchyDbContext> testContext)
+    public TablePerHierarchyReadTests(IntegrationTestContext<TestableStartup<TablePerHierarchyDbContext>, TablePerHierarchyDbContext> testContext)
         : base(testContext)
     {
     }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeReadTests.cs
similarity index 53%
rename from test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeTests.cs
rename to test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeReadTests.cs
index 34f7abe19f..7782f4f315 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeTests.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeReadTests.cs
@@ -4,9 +4,9 @@
 namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerType;
 
 [UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
-public sealed class TablePerTypeTests : ResourceInheritanceTests<TablePerTypeDbContext>
+public sealed class TablePerTypeReadTests : ResourceInheritanceReadTests<TablePerTypeDbContext>
 {
-    public TablePerTypeTests(IntegrationTestContext<TestableStartup<TablePerTypeDbContext>, TablePerTypeDbContext> testContext)
+    public TablePerTypeReadTests(IntegrationTestContext<TestableStartup<TablePerTypeDbContext>, TablePerTypeDbContext> testContext)
         : base(testContext)
     {
     }

From 4d34dcde96c1305a1e6403108c4e9ffe009a90f6 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Wed, 30 Mar 2022 16:16:43 +0200
Subject: [PATCH 13/19] Added extension method to obtain ClrType of a resource
 instance (we'll need this later)

---
 .../AtomicOperations/LocalIdValidator.cs            |  2 +-
 .../AtomicOperations/OperationsProcessor.cs         |  2 +-
 .../Controllers/BaseJsonApiOperationsController.cs  |  3 ++-
 .../Repositories/DbContextExtensions.cs             |  2 +-
 .../Resources/IdentifiableComparer.cs               |  4 ++--
 .../Resources/IdentifiableExtensions.cs             | 13 ++++++++++---
 .../Resources/ResourceDefinitionAccessor.cs         |  4 ++--
 .../Response/ResourceObjectTreeNode.cs              |  8 ++++----
 .../Serialization/Response/ResponseModelAdapter.cs  |  2 +-
 9 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/src/JsonApiDotNetCore/AtomicOperations/LocalIdValidator.cs b/src/JsonApiDotNetCore/AtomicOperations/LocalIdValidator.cs
index cbbc702d0c..9cb463ab10 100644
--- a/src/JsonApiDotNetCore/AtomicOperations/LocalIdValidator.cs
+++ b/src/JsonApiDotNetCore/AtomicOperations/LocalIdValidator.cs
@@ -96,7 +96,7 @@ private void AssertLocalIdIsAssigned(IIdentifiable resource)
     {
         if (resource.LocalId != null)
         {
-            ResourceType resourceType = _resourceGraph.GetResourceType(resource.GetType());
+            ResourceType resourceType = _resourceGraph.GetResourceType(resource.GetClrType());
             _localIdTracker.GetValue(resource.LocalId, resourceType);
         }
     }
diff --git a/src/JsonApiDotNetCore/AtomicOperations/OperationsProcessor.cs b/src/JsonApiDotNetCore/AtomicOperations/OperationsProcessor.cs
index 4a26e36710..6524252abf 100644
--- a/src/JsonApiDotNetCore/AtomicOperations/OperationsProcessor.cs
+++ b/src/JsonApiDotNetCore/AtomicOperations/OperationsProcessor.cs
@@ -140,7 +140,7 @@ private void AssignStringId(IIdentifiable resource)
     {
         if (resource.LocalId != null)
         {
-            ResourceType resourceType = _resourceGraph.GetResourceType(resource.GetType());
+            ResourceType resourceType = _resourceGraph.GetResourceType(resource.GetClrType());
             resource.StringId = _localIdTracker.GetValue(resource.LocalId, resourceType);
         }
     }
diff --git a/src/JsonApiDotNetCore/Controllers/BaseJsonApiOperationsController.cs b/src/JsonApiDotNetCore/Controllers/BaseJsonApiOperationsController.cs
index debcfa5c6f..a948d67edc 100644
--- a/src/JsonApiDotNetCore/Controllers/BaseJsonApiOperationsController.cs
+++ b/src/JsonApiDotNetCore/Controllers/BaseJsonApiOperationsController.cs
@@ -148,7 +148,8 @@ protected virtual void ValidateModelState(IList<OperationContainer> operations)
             Dictionary<string, ModelStateEntry?> modelStateDictionary = requestModelState.ToDictionary(tuple => tuple.key, tuple => tuple.entry);
 
             throw new InvalidModelStateException(modelStateDictionary, typeof(IList<OperationContainer>), _options.IncludeExceptionStackTraceInErrors,
-                _resourceGraph, (collectionType, index) => collectionType == typeof(IList<OperationContainer>) ? operations[index].Resource.GetType() : null);
+                _resourceGraph,
+                (collectionType, index) => collectionType == typeof(IList<OperationContainer>) ? operations[index].Resource.GetClrType() : null);
         }
     }
 
diff --git a/src/JsonApiDotNetCore/Repositories/DbContextExtensions.cs b/src/JsonApiDotNetCore/Repositories/DbContextExtensions.cs
index e9a9488b7b..cadbd658a8 100644
--- a/src/JsonApiDotNetCore/Repositories/DbContextExtensions.cs
+++ b/src/JsonApiDotNetCore/Repositories/DbContextExtensions.cs
@@ -35,7 +35,7 @@ public static IIdentifiable GetTrackedOrAttach(this DbContext dbContext, IIdenti
         ArgumentGuard.NotNull(dbContext, nameof(dbContext));
         ArgumentGuard.NotNull(identifiable, nameof(identifiable));
 
-        Type resourceClrType = identifiable.GetType();
+        Type resourceClrType = identifiable.GetClrType();
         string? stringId = identifiable.StringId;
 
         EntityEntry? entityEntry = dbContext.ChangeTracker.Entries().FirstOrDefault(entry => IsResource(entry, resourceClrType, stringId));
diff --git a/src/JsonApiDotNetCore/Resources/IdentifiableComparer.cs b/src/JsonApiDotNetCore/Resources/IdentifiableComparer.cs
index a59dc8f15f..8a6bed2f91 100644
--- a/src/JsonApiDotNetCore/Resources/IdentifiableComparer.cs
+++ b/src/JsonApiDotNetCore/Resources/IdentifiableComparer.cs
@@ -22,7 +22,7 @@ public bool Equals(IIdentifiable? left, IIdentifiable? right)
             return true;
         }
 
-        if (left is null || right is null || left.GetType() != right.GetType())
+        if (left is null || right is null || left.GetClrType() != right.GetClrType())
         {
             return false;
         }
@@ -38,6 +38,6 @@ public bool Equals(IIdentifiable? left, IIdentifiable? right)
     public int GetHashCode(IIdentifiable obj)
     {
         // LocalId is intentionally omitted here, it is okay for hashes to collide.
-        return HashCode.Combine(obj.GetType(), obj.StringId);
+        return HashCode.Combine(obj.GetClrType(), obj.StringId);
     }
 }
diff --git a/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs b/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs
index 7e8064826a..7e196c68d8 100644
--- a/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs
+++ b/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs
@@ -11,11 +11,11 @@ public static object GetTypedId(this IIdentifiable identifiable)
     {
         ArgumentGuard.NotNull(identifiable, nameof(identifiable));
 
-        PropertyInfo? property = identifiable.GetType().GetProperty(IdPropertyName);
+        PropertyInfo? property = identifiable.GetClrType().GetProperty(IdPropertyName);
 
         if (property == null)
         {
-            throw new InvalidOperationException($"Resource of type '{identifiable.GetType()}' does not contain a property named '{IdPropertyName}'.");
+            throw new InvalidOperationException($"Resource of type '{identifiable.GetClrType()}' does not contain a property named '{IdPropertyName}'.");
         }
 
         object? propertyValue = property.GetValue(identifiable);
@@ -27,11 +27,18 @@ public static object GetTypedId(this IIdentifiable identifiable)
 
             if (Equals(propertyValue, defaultValue))
             {
-                throw new InvalidOperationException($"Property '{identifiable.GetType().Name}.{IdPropertyName}' should " +
+                throw new InvalidOperationException($"Property '{identifiable.GetClrType().Name}.{IdPropertyName}' should " +
                     $"have been assigned at this point, but it contains its default {property.PropertyType.Name} value '{propertyValue}'.");
             }
         }
 
         return propertyValue!;
     }
+
+    public static Type GetClrType(this IIdentifiable identifiable)
+    {
+        ArgumentGuard.NotNull(identifiable, nameof(identifiable));
+
+        return identifiable.GetType();
+    }
 }
diff --git a/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs b/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs
index a16b04cfea..bbea9e7d87 100644
--- a/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs
+++ b/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs
@@ -183,7 +183,7 @@ public void OnDeserialize(IIdentifiable resource)
     {
         ArgumentGuard.NotNull(resource, nameof(resource));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(resource.GetType());
+        dynamic resourceDefinition = ResolveResourceDefinition(resource.GetClrType());
         resourceDefinition.OnDeserialize((dynamic)resource);
     }
 
@@ -192,7 +192,7 @@ public void OnSerialize(IIdentifiable resource)
     {
         ArgumentGuard.NotNull(resource, nameof(resource));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(resource.GetType());
+        dynamic resourceDefinition = ResolveResourceDefinition(resource.GetClrType());
         resourceDefinition.OnSerialize((dynamic)resource);
     }
 
diff --git a/src/JsonApiDotNetCore/Serialization/Response/ResourceObjectTreeNode.cs b/src/JsonApiDotNetCore/Serialization/Response/ResourceObjectTreeNode.cs
index df75fcaa66..f18eeb8913 100644
--- a/src/JsonApiDotNetCore/Serialization/Response/ResourceObjectTreeNode.cs
+++ b/src/JsonApiDotNetCore/Serialization/Response/ResourceObjectTreeNode.cs
@@ -251,19 +251,19 @@ private ResourceObjectComparer()
         {
         }
 
-        public bool Equals(ResourceObject? x, ResourceObject? y)
+        public bool Equals(ResourceObject? left, ResourceObject? right)
         {
-            if (ReferenceEquals(x, y))
+            if (ReferenceEquals(left, right))
             {
                 return true;
             }
 
-            if (x is null || y is null || x.GetType() != y.GetType())
+            if (left is null || right is null || left.GetType() != right.GetType())
             {
                 return false;
             }
 
-            return x.Type == y.Type && x.Id == y.Id && x.Lid == y.Lid;
+            return left.Type == right.Type && left.Id == right.Id && left.Lid == right.Lid;
         }
 
         public int GetHashCode(ResourceObject obj)
diff --git a/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs b/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
index 4045d2c0c0..af1a78bee1 100644
--- a/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
+++ b/src/JsonApiDotNetCore/Serialization/Response/ResponseModelAdapter.cs
@@ -187,7 +187,7 @@ private ResourceObjectTreeNode GetOrCreateTreeNode(IIdentifiable resource, Resou
 
     private static ResourceType GetEffectiveResourceType(IIdentifiable resource, ResourceType declaredType)
     {
-        Type runtimeResourceType = resource.GetType();
+        Type runtimeResourceType = resource.GetClrType();
 
         if (declaredType.ClrType == runtimeResourceType)
         {

From d12eec7e1e1b67f4da19537bf0b479d043788044 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Wed, 30 Mar 2022 16:46:01 +0200
Subject: [PATCH 14/19] Resource inheritance: write endpoints

---
 .../SerializationBenchmarkBase.cs             |    4 +-
 .../Configuration/ResourceType.cs             |   42 +
 .../Queries/Internal/QueryLayerComposer.cs    |    4 +-
 .../EntityFrameworkCoreRepository.cs          |   58 +-
 .../IResourceRepositoryAccessor.cs            |   21 +-
 .../Repositories/IResourceWriteRepository.cs  |    6 +-
 .../ResourceRepositoryAccessor.cs             |   13 +-
 .../Resources/AbstractResourceWrapper.cs      |   15 +
 .../Resources/IAbstractResourceWrapper.cs     |   12 +
 .../Resources/IResourceDefinition.cs          |   25 +-
 .../Resources/IResourceDefinitionAccessor.cs  |    4 +-
 .../Resources/IdentifiableExtensions.cs       |    2 +-
 .../Resources/JsonApiResourceDefinition.cs    |    2 +-
 .../Resources/ResourceChangeTracker.cs        |   14 +-
 .../Resources/ResourceDefinitionAccessor.cs   |   34 +-
 .../Resources/ResourceFactory.cs              |   29 +
 .../Adapters/ResourceIdentityAdapter.cs       |   14 +
 .../Services/JsonApiResourceService.cs        |  184 +-
 .../Transactions/PerformerRepository.cs       |    6 +-
 .../EagerLoading/BuildingRepository.cs        |    4 +-
 .../HitCountingResourceDefinition.cs          |    4 +-
 .../FireForgetTests.Group.cs                  |    1 +
 .../Microservices/MessagingGroupDefinition.cs |   10 +-
 .../OutboxTests.Group.cs                      |    1 +
 .../ChangeTracking/ChangeTrackingDbContext.cs |   16 +
 .../ResourceInheritanceChangeTrackerTests.cs  |   62 +
 .../Models/AlwaysMovingTandem.cs              |   18 +
 .../Models/VehicleManufacturer.cs             |    2 +-
 .../ResourceInheritanceDbContext.cs           |    6 +
 .../ResourceInheritanceFakers.cs              |    8 +
 .../ResourceInheritanceWriteTests.cs          | 2741 +++++++++++++++++
 .../ResourceTypeCaptureStore.cs               |   44 +
 .../ResourceTypeCapturingDefinition.cs        |  120 +
 .../TablePerHierarchyWriteTests.cs            |   13 +
 .../TablePerType/TablePerTypeWriteTests.cs    |   13 +
 .../FakeResourceDefinitionAccessor.cs         |    4 +-
 .../ServiceCollectionExtensionsTests.cs       |   18 +-
 37 files changed, 3453 insertions(+), 121 deletions(-)
 create mode 100644 src/JsonApiDotNetCore/Resources/AbstractResourceWrapper.cs
 create mode 100644 src/JsonApiDotNetCore/Resources/IAbstractResourceWrapper.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ChangeTrackingDbContext.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ResourceInheritanceChangeTrackerTests.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/AlwaysMovingTandem.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceWriteTests.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCaptureStore.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCapturingDefinition.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyWriteTests.cs
 create mode 100644 test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeWriteTests.cs

diff --git a/benchmarks/Serialization/SerializationBenchmarkBase.cs b/benchmarks/Serialization/SerializationBenchmarkBase.cs
index befa5049e8..100ff60e25 100644
--- a/benchmarks/Serialization/SerializationBenchmarkBase.cs
+++ b/benchmarks/Serialization/SerializationBenchmarkBase.cs
@@ -180,9 +180,9 @@ public Task OnSetToManyRelationshipAsync<TResource>(TResource leftResource, HasM
             return Task.CompletedTask;
         }
 
-        public Task OnAddToRelationshipAsync<TResource, TId>(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        public Task OnAddToRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
             CancellationToken cancellationToken)
-            where TResource : class, IIdentifiable<TId>
+            where TResource : class, IIdentifiable
         {
             return Task.CompletedTask;
         }
diff --git a/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs b/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
index 83491d5c22..c9b2f8064d 100644
--- a/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
+++ b/src/JsonApiDotNetCore.Annotations/Configuration/ResourceType.cs
@@ -206,6 +206,43 @@ public IReadOnlySet<ResourceType> GetAllConcreteDerivedTypes()
         return _lazyAllConcreteDerivedTypes.Value;
     }
 
+    /// <summary>
+    /// Searches the tree of derived types to find a match for the specified <paramref name="clrType" />.
+    /// </summary>
+    public ResourceType GetTypeOrDerived(Type clrType)
+    {
+        ArgumentGuard.NotNull(clrType, nameof(clrType));
+
+        ResourceType? derivedType = FindTypeOrDerived(this, clrType);
+
+        if (derivedType == null)
+        {
+            throw new InvalidOperationException($"Resource type '{PublicName}' is not a base type of '{clrType}'.");
+        }
+
+        return derivedType;
+    }
+
+    private static ResourceType? FindTypeOrDerived(ResourceType type, Type clrType)
+    {
+        if (type.ClrType == clrType)
+        {
+            return type;
+        }
+
+        foreach (ResourceType derivedType in type.DirectlyDerivedTypes)
+        {
+            ResourceType? matchingType = FindTypeOrDerived(derivedType, clrType);
+
+            if (matchingType != null)
+            {
+                return matchingType;
+            }
+        }
+
+        return null;
+    }
+
     internal IReadOnlySet<AttrAttribute> GetAttributesInTypeOrDerived(string publicName)
     {
         return GetAttributesInTypeOrDerived(this, publicName);
@@ -261,6 +298,11 @@ private static IReadOnlySet<RelationshipAttribute> GetRelationshipsInTypeOrDeriv
         return relationshipsInDerivedTypes;
     }
 
+    internal bool IsPartOfTypeHierarchy()
+    {
+        return BaseType != null || DirectlyDerivedTypes.Any();
+    }
+
     public override string ToString()
     {
         return PublicName;
diff --git a/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs b/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs
index 253e65012c..00181a23a7 100644
--- a/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs
+++ b/src/JsonApiDotNetCore/Queries/Internal/QueryLayerComposer.cs
@@ -422,7 +422,7 @@ public QueryLayer ComposeForGetRelationshipRightIds(RelationshipAttribute relati
 
         AttrAttribute rightIdAttribute = GetIdAttribute(relationship.RightType);
 
-        object[] typedIds = rightResourceIds.Select(resource => resource.GetTypedId()).ToArray();
+        HashSet<object> typedIds = rightResourceIds.Select(resource => resource.GetTypedId()).ToHashSet();
 
         FilterExpression? baseFilter = GetFilter(Array.Empty<QueryExpression>(), relationship.RightType);
         FilterExpression? filter = CreateFilterByIds(typedIds, rightIdAttribute, baseFilter);
@@ -447,7 +447,7 @@ public QueryLayer ComposeForHasMany<TId>(HasManyAttribute hasManyRelationship, T
 
         AttrAttribute leftIdAttribute = GetIdAttribute(hasManyRelationship.LeftType);
         AttrAttribute rightIdAttribute = GetIdAttribute(hasManyRelationship.RightType);
-        object[] rightTypedIds = rightResourceIds.Select(resource => resource.GetTypedId()).ToArray();
+        HashSet<object> rightTypedIds = rightResourceIds.Select(resource => resource.GetTypedId()).ToHashSet();
 
         FilterExpression? leftFilter = CreateFilterByIds(leftId.AsArray(), leftIdAttribute, null);
         FilterExpression? rightFilter = CreateFilterByIds(rightTypedIds, rightIdAttribute, null);
diff --git a/src/JsonApiDotNetCore/Repositories/EntityFrameworkCoreRepository.cs b/src/JsonApiDotNetCore/Repositories/EntityFrameworkCoreRepository.cs
index 52c07c5244..50c9e07ea3 100644
--- a/src/JsonApiDotNetCore/Repositories/EntityFrameworkCoreRepository.cs
+++ b/src/JsonApiDotNetCore/Repositories/EntityFrameworkCoreRepository.cs
@@ -155,14 +155,15 @@ protected virtual IQueryable<TResource> GetAll()
     }
 
     /// <inheritdoc />
-    public virtual Task<TResource> GetForCreateAsync(TId id, CancellationToken cancellationToken)
+    public virtual Task<TResource> GetForCreateAsync(Type resourceClrType, TId id, CancellationToken cancellationToken)
     {
         _traceWriter.LogMethodStart(new
         {
+            resourceClrType,
             id
         });
 
-        var resource = _resourceFactory.CreateInstance<TResource>();
+        var resource = (TResource)_resourceFactory.CreateInstance(resourceClrType);
         resource.Id = id;
 
         return Task.FromResult(resource);
@@ -305,10 +306,11 @@ protected void AssertIsNotClearingRequiredToOneRelationship(RelationshipAttribut
     }
 
     /// <inheritdoc />
-    public virtual async Task DeleteAsync(TId id, CancellationToken cancellationToken)
+    public virtual async Task DeleteAsync(TResource? resourceFromDatabase, TId id, CancellationToken cancellationToken)
     {
         _traceWriter.LogMethodStart(new
         {
+            resourceFromDatabase,
             id
         });
 
@@ -316,7 +318,7 @@ public virtual async Task DeleteAsync(TId id, CancellationToken cancellationToke
 
         // This enables OnWritingAsync() to fetch the resource, which adds it to the change tracker.
         // If so, we'll reuse the tracked resource instead of this placeholder resource.
-        var placeholderResource = _resourceFactory.CreateInstance<TResource>();
+        TResource placeholderResource = resourceFromDatabase ?? _resourceFactory.CreateInstance<TResource>();
         placeholderResource.Id = id;
 
         await _resourceDefinitionAccessor.OnWritingAsync(placeholderResource, WriteOperationKind.DeleteResource, cancellationToken);
@@ -413,10 +415,12 @@ public virtual async Task SetRelationshipAsync(TResource leftResource, object? r
     }
 
     /// <inheritdoc />
-    public virtual async Task AddToToManyRelationshipAsync(TId leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
+    public virtual async Task AddToToManyRelationshipAsync(TResource? leftResource, TId leftId, ISet<IIdentifiable> rightResourceIds,
+        CancellationToken cancellationToken)
     {
         _traceWriter.LogMethodStart(new
         {
+            leftResource,
             leftId,
             rightResourceIds
         });
@@ -427,18 +431,22 @@ public virtual async Task AddToToManyRelationshipAsync(TId leftId, ISet<IIdentif
 
         var relationship = (HasManyAttribute)_targetedFields.Relationships.Single();
 
-        await _resourceDefinitionAccessor.OnAddToRelationshipAsync<TResource, TId>(leftId, relationship, rightResourceIds, cancellationToken);
+        // This enables OnAddToRelationshipAsync() or OnWritingAsync() to fetch the resource, which adds it to the change tracker.
+        // If so, we'll reuse the tracked resource instead of this placeholder resource.
+        TResource leftPlaceholderResource = leftResource ?? _resourceFactory.CreateInstance<TResource>();
+        leftPlaceholderResource.Id = leftId;
+
+        await _resourceDefinitionAccessor.OnAddToRelationshipAsync(leftPlaceholderResource, relationship, rightResourceIds, cancellationToken);
 
         if (rightResourceIds.Any())
         {
-            var leftPlaceholderResource = _resourceFactory.CreateInstance<TResource>();
-            leftPlaceholderResource.Id = leftId;
-
             var leftResourceTracked = (TResource)_dbContext.GetTrackedOrAttach(leftPlaceholderResource);
+            IEnumerable rightValueToStore = GetRightValueToStoreForAddToToMany(leftResourceTracked, relationship, rightResourceIds);
 
-            await UpdateRelationshipAsync(relationship, leftResourceTracked, rightResourceIds, cancellationToken);
+            await UpdateRelationshipAsync(relationship, leftResourceTracked, rightValueToStore, cancellationToken);
 
             await _resourceDefinitionAccessor.OnWritingAsync(leftResourceTracked, WriteOperationKind.AddToRelationship, cancellationToken);
+            leftResourceTracked = (TResource)_dbContext.GetTrackedOrAttach(leftResourceTracked);
 
             await SaveChangesAsync(cancellationToken);
 
@@ -446,6 +454,30 @@ public virtual async Task AddToToManyRelationshipAsync(TId leftId, ISet<IIdentif
         }
     }
 
+    private IEnumerable GetRightValueToStoreForAddToToMany(TResource leftResource, HasManyAttribute relationship, ISet<IIdentifiable> rightResourceIdsToAdd)
+    {
+        object? rightValueStored = relationship.GetValue(leftResource);
+
+        // @formatter:wrap_chained_method_calls chop_always
+        // @formatter:keep_existing_linebreaks true
+
+        HashSet<IIdentifiable> rightResourceIdsStored = _collectionConverter
+            .ExtractResources(rightValueStored)
+            .Select(rightResource => _dbContext.GetTrackedOrAttach(rightResource))
+            .ToHashSet(IdentifiableComparer.Instance);
+
+        // @formatter:keep_existing_linebreaks restore
+        // @formatter:wrap_chained_method_calls restore
+
+        if (rightResourceIdsStored.Any())
+        {
+            rightResourceIdsStored.AddRange(rightResourceIdsToAdd);
+            return rightResourceIdsStored;
+        }
+
+        return rightResourceIdsToAdd;
+    }
+
     /// <inheritdoc />
     public virtual async Task RemoveFromToManyRelationshipAsync(TResource leftResource, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken)
@@ -473,7 +505,7 @@ public virtual async Task RemoveFromToManyRelationshipAsync(TResource leftResour
             // Make Entity Framework Core believe any additional resources added from ResourceDefinition already exist in database.
             IIdentifiable[] extraResourceIdsToRemove = rightResourceIdsToRemove.Where(rightId => !rightResourceIds.Contains(rightId)).ToArray();
 
-            object? rightValueStored = relationship.GetValue(leftResource);
+            object? rightValueStored = relationship.GetValue(leftResourceTracked);
 
             // @formatter:wrap_chained_method_calls chop_always
             // @formatter:keep_existing_linebreaks true
@@ -488,9 +520,9 @@ public virtual async Task RemoveFromToManyRelationshipAsync(TResource leftResour
             // @formatter:wrap_chained_method_calls restore
 
             rightValueStored = _collectionConverter.CopyToTypedCollection(rightResourceIdsStored, relationship.Property.PropertyType);
-            relationship.SetValue(leftResource, rightValueStored);
+            relationship.SetValue(leftResourceTracked, rightValueStored);
 
-            MarkRelationshipAsLoaded(leftResource, relationship);
+            MarkRelationshipAsLoaded(leftResourceTracked, relationship);
 
             HashSet<IIdentifiable> rightResourceIdsToStore = rightResourceIdsStored.ToHashSet(IdentifiableComparer.Instance);
             rightResourceIdsToStore.ExceptWith(rightResourceIdsToRemove);
diff --git a/src/JsonApiDotNetCore/Repositories/IResourceRepositoryAccessor.cs b/src/JsonApiDotNetCore/Repositories/IResourceRepositoryAccessor.cs
index 9654365121..149fef1cfb 100644
--- a/src/JsonApiDotNetCore/Repositories/IResourceRepositoryAccessor.cs
+++ b/src/JsonApiDotNetCore/Repositories/IResourceRepositoryAccessor.cs
@@ -11,7 +11,7 @@ namespace JsonApiDotNetCore.Repositories;
 public interface IResourceRepositoryAccessor
 {
     /// <summary>
-    /// Invokes <see cref="IResourceReadRepository{TResource,TId}.GetAsync" />.
+    /// Invokes <see cref="IResourceReadRepository{TResource,TId}.GetAsync" /> for the specified resource type.
     /// </summary>
     Task<IReadOnlyCollection<TResource>> GetAsync<TResource>(QueryLayer queryLayer, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable;
@@ -27,25 +27,25 @@ Task<IReadOnlyCollection<TResource>> GetAsync<TResource>(QueryLayer queryLayer,
     Task<int> CountAsync(ResourceType resourceType, FilterExpression? filter, CancellationToken cancellationToken);
 
     /// <summary>
-    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.GetForCreateAsync" />.
+    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.GetForCreateAsync" /> for the specified resource type.
     /// </summary>
-    Task<TResource> GetForCreateAsync<TResource, TId>(TId id, CancellationToken cancellationToken)
+    Task<TResource> GetForCreateAsync<TResource, TId>(Type resourceClrType, TId id, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable<TId>;
 
     /// <summary>
-    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.CreateAsync" />.
+    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.CreateAsync" /> for the specified resource type.
     /// </summary>
     Task CreateAsync<TResource>(TResource resourceFromRequest, TResource resourceForDatabase, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable;
 
     /// <summary>
-    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.GetForUpdateAsync" />.
+    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.GetForUpdateAsync" /> for the specified resource type.
     /// </summary>
     Task<TResource?> GetForUpdateAsync<TResource>(QueryLayer queryLayer, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable;
 
     /// <summary>
-    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.UpdateAsync" />.
+    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.UpdateAsync" /> for the specified resource type.
     /// </summary>
     Task UpdateAsync<TResource>(TResource resourceFromRequest, TResource resourceFromDatabase, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable;
@@ -53,11 +53,11 @@ Task UpdateAsync<TResource>(TResource resourceFromRequest, TResource resourceFro
     /// <summary>
     /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.DeleteAsync" /> for the specified resource type.
     /// </summary>
-    Task DeleteAsync<TResource, TId>(TId id, CancellationToken cancellationToken)
+    Task DeleteAsync<TResource, TId>(TResource? resourceFromDatabase, TId id, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable<TId>;
 
     /// <summary>
-    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.SetRelationshipAsync" />.
+    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.SetRelationshipAsync" /> for the specified resource type.
     /// </summary>
     Task SetRelationshipAsync<TResource>(TResource leftResource, object? rightValue, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable;
@@ -65,11 +65,12 @@ Task SetRelationshipAsync<TResource>(TResource leftResource, object? rightValue,
     /// <summary>
     /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.AddToToManyRelationshipAsync" /> for the specified resource type.
     /// </summary>
-    Task AddToToManyRelationshipAsync<TResource, TId>(TId leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
+    Task AddToToManyRelationshipAsync<TResource, TId>(TResource? leftResource, TId leftId, ISet<IIdentifiable> rightResourceIds,
+        CancellationToken cancellationToken)
         where TResource : class, IIdentifiable<TId>;
 
     /// <summary>
-    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.RemoveFromToManyRelationshipAsync" />.
+    /// Invokes <see cref="IResourceWriteRepository{TResource,TId}.RemoveFromToManyRelationshipAsync" /> for the specified resource type.
     /// </summary>
     Task RemoveFromToManyRelationshipAsync<TResource>(TResource leftResource, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable;
diff --git a/src/JsonApiDotNetCore/Repositories/IResourceWriteRepository.cs b/src/JsonApiDotNetCore/Repositories/IResourceWriteRepository.cs
index ca0186d5b5..fb0267d18a 100644
--- a/src/JsonApiDotNetCore/Repositories/IResourceWriteRepository.cs
+++ b/src/JsonApiDotNetCore/Repositories/IResourceWriteRepository.cs
@@ -23,7 +23,7 @@ public interface IResourceWriteRepository<TResource, in TId>
     /// <remarks>
     /// This method can be overridden to assign resource-specific required relationships.
     /// </remarks>
-    Task<TResource> GetForCreateAsync(TId id, CancellationToken cancellationToken);
+    Task<TResource> GetForCreateAsync(Type resourceClrType, TId id, CancellationToken cancellationToken);
 
     /// <summary>
     /// Creates a new resource in the underlying data store.
@@ -43,7 +43,7 @@ public interface IResourceWriteRepository<TResource, in TId>
     /// <summary>
     /// Deletes an existing resource from the underlying data store.
     /// </summary>
-    Task DeleteAsync(TId id, CancellationToken cancellationToken);
+    Task DeleteAsync(TResource? resourceFromDatabase, TId id, CancellationToken cancellationToken);
 
     /// <summary>
     /// Performs a complete replacement of the relationship in the underlying data store.
@@ -53,7 +53,7 @@ public interface IResourceWriteRepository<TResource, in TId>
     /// <summary>
     /// Adds resources to a to-many relationship in the underlying data store.
     /// </summary>
-    Task AddToToManyRelationshipAsync(TId leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken);
+    Task AddToToManyRelationshipAsync(TResource? leftResource, TId leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken);
 
     /// <summary>
     /// Removes resources from a to-many relationship in the underlying data store.
diff --git a/src/JsonApiDotNetCore/Repositories/ResourceRepositoryAccessor.cs b/src/JsonApiDotNetCore/Repositories/ResourceRepositoryAccessor.cs
index 0ba96126a1..5f00cdf08d 100644
--- a/src/JsonApiDotNetCore/Repositories/ResourceRepositoryAccessor.cs
+++ b/src/JsonApiDotNetCore/Repositories/ResourceRepositoryAccessor.cs
@@ -53,11 +53,11 @@ public async Task<int> CountAsync(ResourceType resourceType, FilterExpression? f
     }
 
     /// <inheritdoc />
-    public async Task<TResource> GetForCreateAsync<TResource, TId>(TId id, CancellationToken cancellationToken)
+    public async Task<TResource> GetForCreateAsync<TResource, TId>(Type resourceClrType, TId id, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable<TId>
     {
         dynamic repository = GetWriteRepository(typeof(TResource));
-        return await repository.GetForCreateAsync(id, cancellationToken);
+        return await repository.GetForCreateAsync(resourceClrType, id, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -85,11 +85,11 @@ public async Task UpdateAsync<TResource>(TResource resourceFromRequest, TResourc
     }
 
     /// <inheritdoc />
-    public async Task DeleteAsync<TResource, TId>(TId id, CancellationToken cancellationToken)
+    public async Task DeleteAsync<TResource, TId>(TResource? resourceFromDatabase, TId id, CancellationToken cancellationToken)
         where TResource : class, IIdentifiable<TId>
     {
         dynamic repository = GetWriteRepository(typeof(TResource));
-        await repository.DeleteAsync(id, cancellationToken);
+        await repository.DeleteAsync(resourceFromDatabase, id, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -101,11 +101,12 @@ public async Task SetRelationshipAsync<TResource>(TResource leftResource, object
     }
 
     /// <inheritdoc />
-    public async Task AddToToManyRelationshipAsync<TResource, TId>(TId leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
+    public async Task AddToToManyRelationshipAsync<TResource, TId>(TResource? leftResource, TId leftId, ISet<IIdentifiable> rightResourceIds,
+        CancellationToken cancellationToken)
         where TResource : class, IIdentifiable<TId>
     {
         dynamic repository = GetWriteRepository(typeof(TResource));
-        await repository.AddToToManyRelationshipAsync(leftId, rightResourceIds, cancellationToken);
+        await repository.AddToToManyRelationshipAsync(leftResource, leftId, rightResourceIds, cancellationToken);
     }
 
     /// <inheritdoc />
diff --git a/src/JsonApiDotNetCore/Resources/AbstractResourceWrapper.cs b/src/JsonApiDotNetCore/Resources/AbstractResourceWrapper.cs
new file mode 100644
index 0000000000..0d294feb57
--- /dev/null
+++ b/src/JsonApiDotNetCore/Resources/AbstractResourceWrapper.cs
@@ -0,0 +1,15 @@
+namespace JsonApiDotNetCore.Resources;
+
+/// <inheritdoc cref="IAbstractResourceWrapper" />
+internal sealed class AbstractResourceWrapper<TId> : Identifiable<TId>, IAbstractResourceWrapper
+{
+    /// <inheritdoc />
+    public Type AbstractType { get; }
+
+    public AbstractResourceWrapper(Type abstractType)
+    {
+        ArgumentGuard.NotNull(abstractType, nameof(abstractType));
+
+        AbstractType = abstractType;
+    }
+}
diff --git a/src/JsonApiDotNetCore/Resources/IAbstractResourceWrapper.cs b/src/JsonApiDotNetCore/Resources/IAbstractResourceWrapper.cs
new file mode 100644
index 0000000000..7e9ac3c71d
--- /dev/null
+++ b/src/JsonApiDotNetCore/Resources/IAbstractResourceWrapper.cs
@@ -0,0 +1,12 @@
+namespace JsonApiDotNetCore.Resources;
+
+/// <summary>
+/// Because an instance cannot be created from an abstract resource type, this wrapper is used to preserve that information.
+/// </summary>
+internal interface IAbstractResourceWrapper : IIdentifiable
+{
+    /// <summary>
+    /// The abstract resource type.
+    /// </summary>
+    Type AbstractType { get; }
+}
diff --git a/src/JsonApiDotNetCore/Resources/IResourceDefinition.cs b/src/JsonApiDotNetCore/Resources/IResourceDefinition.cs
index 1a61868de5..2315ee7b1a 100644
--- a/src/JsonApiDotNetCore/Resources/IResourceDefinition.cs
+++ b/src/JsonApiDotNetCore/Resources/IResourceDefinition.cs
@@ -133,9 +133,9 @@ public interface IResourceDefinition<TResource, in TId>
     /// </param>
     /// <param name="writeOperation">
     /// Identifies the logical write operation for which this method was called. Possible values: <see cref="WriteOperationKind.CreateResource" />,
-    /// <see cref="WriteOperationKind.UpdateResource" /> and <see cref="WriteOperationKind.SetRelationship" />. Note this intentionally excludes
-    /// <see cref="WriteOperationKind.DeleteResource" />, <see cref="WriteOperationKind.AddToRelationship" /> and
-    /// <see cref="WriteOperationKind.RemoveFromRelationship" />, because for those endpoints no resource is retrieved upfront.
+    /// <see cref="WriteOperationKind.UpdateResource" />, <see cref="WriteOperationKind.SetRelationship" /> and
+    /// <see cref="WriteOperationKind.RemoveFromRelationship" />. Note this intentionally excludes <see cref="WriteOperationKind.DeleteResource" /> and
+    /// <see cref="WriteOperationKind.AddToRelationship" />, because for those endpoints no resource is retrieved upfront.
     /// </param>
     /// <param name="cancellationToken">
     /// Propagates notification that request handling should be canceled.
@@ -203,9 +203,22 @@ Task OnSetToManyRelationshipAsync(TResource leftResource, HasManyAttribute hasMa
     /// Implementing this method enables to perform validations and make changes to <paramref name="rightResourceIds" />, before the relationship is updated.
     /// </para>
     /// </summary>
-    /// <param name="leftResourceId">
+    /// <param name="leftResource">
     /// Identifier of the left resource. The indication "left" specifies that <paramref name="hasManyRelationship" /> is declared on
-    /// <typeparamref name="TResource" />.
+    /// <typeparamref name="TResource" />. In contrast to other relationship methods, this value is not retrieved from the underlying data store, except in
+    /// the following two cases:
+    /// <list type="bullet">
+    /// <item>
+    /// <description>
+    /// <paramref name="hasManyRelationship" /> is a many-to-many relationship. This is required to prevent failure when already assigned.
+    /// </description>
+    /// </item>
+    /// <item>
+    /// <description>
+    /// The left resource type is part of a type hierarchy. This ensures your business logic runs against the actually stored type.
+    /// </description>
+    /// </item>
+    /// </list>
     /// </param>
     /// <param name="hasManyRelationship">
     /// The to-many relationship being added to.
@@ -216,7 +229,7 @@ Task OnSetToManyRelationshipAsync(TResource leftResource, HasManyAttribute hasMa
     /// <param name="cancellationToken">
     /// Propagates notification that request handling should be canceled.
     /// </param>
-    Task OnAddToRelationshipAsync(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+    Task OnAddToRelationshipAsync(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken);
 
     /// <summary>
diff --git a/src/JsonApiDotNetCore/Resources/IResourceDefinitionAccessor.cs b/src/JsonApiDotNetCore/Resources/IResourceDefinitionAccessor.cs
index a6d229609a..edba16d045 100644
--- a/src/JsonApiDotNetCore/Resources/IResourceDefinitionAccessor.cs
+++ b/src/JsonApiDotNetCore/Resources/IResourceDefinitionAccessor.cs
@@ -70,9 +70,9 @@ public Task OnSetToManyRelationshipAsync<TResource>(TResource leftResource, HasM
     /// <summary>
     /// Invokes <see cref="IResourceDefinition{TResource,TId}.OnAddToRelationshipAsync" /> for the specified resource.
     /// </summary>
-    public Task OnAddToRelationshipAsync<TResource, TId>(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+    public Task OnAddToRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken)
-        where TResource : class, IIdentifiable<TId>;
+        where TResource : class, IIdentifiable;
 
     /// <summary>
     /// Invokes <see cref="IResourceDefinition{TResource,TId}.OnRemoveFromRelationshipAsync" /> for the specified resource.
diff --git a/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs b/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs
index 7e196c68d8..8c9d4b6a36 100644
--- a/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs
+++ b/src/JsonApiDotNetCore/Resources/IdentifiableExtensions.cs
@@ -39,6 +39,6 @@ public static Type GetClrType(this IIdentifiable identifiable)
     {
         ArgumentGuard.NotNull(identifiable, nameof(identifiable));
 
-        return identifiable.GetType();
+        return identifiable is IAbstractResourceWrapper abstractResource ? abstractResource.AbstractType : identifiable.GetType();
     }
 }
diff --git a/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs b/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs
index 0050886112..dbb90bf6fe 100644
--- a/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs
+++ b/src/JsonApiDotNetCore/Resources/JsonApiResourceDefinition.cs
@@ -138,7 +138,7 @@ public virtual Task OnSetToManyRelationshipAsync(TResource leftResource, HasMany
     }
 
     /// <inheritdoc />
-    public virtual Task OnAddToRelationshipAsync(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+    public virtual Task OnAddToRelationshipAsync(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken)
     {
         return Task.CompletedTask;
diff --git a/src/JsonApiDotNetCore/Resources/ResourceChangeTracker.cs b/src/JsonApiDotNetCore/Resources/ResourceChangeTracker.cs
index 7ccd381456..658e5e2c5b 100644
--- a/src/JsonApiDotNetCore/Resources/ResourceChangeTracker.cs
+++ b/src/JsonApiDotNetCore/Resources/ResourceChangeTracker.cs
@@ -1,6 +1,6 @@
 using System.Text.Json;
 using JetBrains.Annotations;
-using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Middleware;
 using JsonApiDotNetCore.Resources.Annotations;
 
 namespace JsonApiDotNetCore.Resources;
@@ -10,19 +10,19 @@ namespace JsonApiDotNetCore.Resources;
 public sealed class ResourceChangeTracker<TResource> : IResourceChangeTracker<TResource>
     where TResource : class, IIdentifiable
 {
-    private readonly ResourceType _resourceType;
+    private readonly IJsonApiRequest _request;
     private readonly ITargetedFields _targetedFields;
 
     private IDictionary<string, string>? _initiallyStoredAttributeValues;
     private IDictionary<string, string>? _requestAttributeValues;
     private IDictionary<string, string>? _finallyStoredAttributeValues;
 
-    public ResourceChangeTracker(IResourceGraph resourceGraph, ITargetedFields targetedFields)
+    public ResourceChangeTracker(IJsonApiRequest request, ITargetedFields targetedFields)
     {
-        ArgumentGuard.NotNull(resourceGraph, nameof(resourceGraph));
+        ArgumentGuard.NotNull(request, nameof(request));
         ArgumentGuard.NotNull(targetedFields, nameof(targetedFields));
 
-        _resourceType = resourceGraph.GetResourceType<TResource>();
+        _request = request;
         _targetedFields = targetedFields;
     }
 
@@ -31,7 +31,7 @@ public void SetInitiallyStoredAttributeValues(TResource resource)
     {
         ArgumentGuard.NotNull(resource, nameof(resource));
 
-        _initiallyStoredAttributeValues = CreateAttributeDictionary(resource, _resourceType.Attributes);
+        _initiallyStoredAttributeValues = CreateAttributeDictionary(resource, _request.PrimaryResourceType!.Attributes);
     }
 
     /// <inheritdoc />
@@ -47,7 +47,7 @@ public void SetFinallyStoredAttributeValues(TResource resource)
     {
         ArgumentGuard.NotNull(resource, nameof(resource));
 
-        _finallyStoredAttributeValues = CreateAttributeDictionary(resource, _resourceType.Attributes);
+        _finallyStoredAttributeValues = CreateAttributeDictionary(resource, _request.PrimaryResourceType!.Attributes);
     }
 
     private IDictionary<string, string> CreateAttributeDictionary(TResource resource, IEnumerable<AttrAttribute> attributes)
diff --git a/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs b/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs
index bbea9e7d87..9f8dfdddeb 100644
--- a/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs
+++ b/src/JsonApiDotNetCore/Resources/ResourceDefinitionAccessor.cs
@@ -104,8 +104,8 @@ public async Task OnPrepareWriteAsync<TResource>(TResource resource, WriteOperat
     {
         ArgumentGuard.NotNull(resource, nameof(resource));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(typeof(TResource));
-        await resourceDefinition.OnPrepareWriteAsync(resource, writeOperation, cancellationToken);
+        dynamic resourceDefinition = ResolveResourceDefinition(resource.GetClrType());
+        await resourceDefinition.OnPrepareWriteAsync((dynamic)resource, writeOperation, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -116,8 +116,10 @@ public async Task OnPrepareWriteAsync<TResource>(TResource resource, WriteOperat
         ArgumentGuard.NotNull(leftResource, nameof(leftResource));
         ArgumentGuard.NotNull(hasOneRelationship, nameof(hasOneRelationship));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(typeof(TResource));
-        return await resourceDefinition.OnSetToOneRelationshipAsync(leftResource, hasOneRelationship, rightResourceId, writeOperation, cancellationToken);
+        dynamic resourceDefinition = ResolveResourceDefinition(leftResource.GetClrType());
+
+        return await resourceDefinition.OnSetToOneRelationshipAsync((dynamic)leftResource, hasOneRelationship, rightResourceId, writeOperation,
+            cancellationToken);
     }
 
     /// <inheritdoc />
@@ -129,20 +131,20 @@ public async Task OnSetToManyRelationshipAsync<TResource>(TResource leftResource
         ArgumentGuard.NotNull(hasManyRelationship, nameof(hasManyRelationship));
         ArgumentGuard.NotNull(rightResourceIds, nameof(rightResourceIds));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(typeof(TResource));
-        await resourceDefinition.OnSetToManyRelationshipAsync(leftResource, hasManyRelationship, rightResourceIds, writeOperation, cancellationToken);
+        dynamic resourceDefinition = ResolveResourceDefinition(leftResource.GetClrType());
+        await resourceDefinition.OnSetToManyRelationshipAsync((dynamic)leftResource, hasManyRelationship, rightResourceIds, writeOperation, cancellationToken);
     }
 
     /// <inheritdoc />
-    public async Task OnAddToRelationshipAsync<TResource, TId>(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+    public async Task OnAddToRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken)
-        where TResource : class, IIdentifiable<TId>
+        where TResource : class, IIdentifiable
     {
         ArgumentGuard.NotNull(hasManyRelationship, nameof(hasManyRelationship));
         ArgumentGuard.NotNull(rightResourceIds, nameof(rightResourceIds));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(typeof(TResource));
-        await resourceDefinition.OnAddToRelationshipAsync(leftResourceId, hasManyRelationship, rightResourceIds, cancellationToken);
+        dynamic resourceDefinition = ResolveResourceDefinition(leftResource.GetClrType());
+        await resourceDefinition.OnAddToRelationshipAsync((dynamic)leftResource, hasManyRelationship, rightResourceIds, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -154,8 +156,8 @@ public async Task OnRemoveFromRelationshipAsync<TResource>(TResource leftResourc
         ArgumentGuard.NotNull(hasManyRelationship, nameof(hasManyRelationship));
         ArgumentGuard.NotNull(rightResourceIds, nameof(rightResourceIds));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(typeof(TResource));
-        await resourceDefinition.OnRemoveFromRelationshipAsync(leftResource, hasManyRelationship, rightResourceIds, cancellationToken);
+        dynamic resourceDefinition = ResolveResourceDefinition(leftResource.GetClrType());
+        await resourceDefinition.OnRemoveFromRelationshipAsync((dynamic)leftResource, hasManyRelationship, rightResourceIds, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -164,8 +166,8 @@ public async Task OnWritingAsync<TResource>(TResource resource, WriteOperationKi
     {
         ArgumentGuard.NotNull(resource, nameof(resource));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(typeof(TResource));
-        await resourceDefinition.OnWritingAsync(resource, writeOperation, cancellationToken);
+        dynamic resourceDefinition = ResolveResourceDefinition(resource.GetClrType());
+        await resourceDefinition.OnWritingAsync((dynamic)resource, writeOperation, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -174,8 +176,8 @@ public async Task OnWriteSucceededAsync<TResource>(TResource resource, WriteOper
     {
         ArgumentGuard.NotNull(resource, nameof(resource));
 
-        dynamic resourceDefinition = ResolveResourceDefinition(typeof(TResource));
-        await resourceDefinition.OnWriteSucceededAsync(resource, writeOperation, cancellationToken);
+        dynamic resourceDefinition = ResolveResourceDefinition(resource.GetClrType());
+        await resourceDefinition.OnWriteSucceededAsync((dynamic)resource, writeOperation, cancellationToken);
     }
 
     /// <inheritdoc />
diff --git a/src/JsonApiDotNetCore/Resources/ResourceFactory.cs b/src/JsonApiDotNetCore/Resources/ResourceFactory.cs
index fa3e571c7c..c276c073cd 100644
--- a/src/JsonApiDotNetCore/Resources/ResourceFactory.cs
+++ b/src/JsonApiDotNetCore/Resources/ResourceFactory.cs
@@ -1,5 +1,6 @@
 using System.Linq.Expressions;
 using System.Reflection;
+using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Queries.Internal;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -8,6 +9,8 @@ namespace JsonApiDotNetCore.Resources;
 /// <inheritdoc />
 internal sealed class ResourceFactory : IResourceFactory
 {
+    private static readonly TypeLocator TypeLocator = new();
+
     private readonly IServiceProvider _serviceProvider;
 
     public ResourceFactory(IServiceProvider serviceProvider)
@@ -22,9 +25,35 @@ public IIdentifiable CreateInstance(Type resourceClrType)
     {
         ArgumentGuard.NotNull(resourceClrType, nameof(resourceClrType));
 
+        if (!resourceClrType.IsAssignableTo(typeof(IIdentifiable)))
+        {
+            throw new InvalidOperationException($"Resource type '{resourceClrType}' does not implement IIdentifiable.");
+        }
+
+        if (resourceClrType.IsAbstract)
+        {
+            return CreateWrapperForAbstractType(resourceClrType);
+        }
+
         return InnerCreateInstance(resourceClrType, _serviceProvider);
     }
 
+    private static IIdentifiable CreateWrapperForAbstractType(Type resourceClrType)
+    {
+        ResourceDescriptor? descriptor = TypeLocator.ResolveResourceDescriptor(resourceClrType);
+
+        if (descriptor == null)
+        {
+            throw new InvalidOperationException($"Resource type '{resourceClrType}' implements 'IIdentifiable', but not 'IIdentifiable<TId>'.");
+        }
+
+        Type wrapperClrType = typeof(AbstractResourceWrapper<>).MakeGenericType(descriptor.IdClrType);
+        ConstructorInfo constructor = wrapperClrType.GetConstructors().Single();
+
+        object resource = constructor.Invoke(ArrayFactory.Create<object>(resourceClrType));
+        return (IIdentifiable)resource;
+    }
+
     /// <inheritdoc />
     public TResource CreateInstance<TResource>()
         where TResource : IIdentifiable
diff --git a/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs b/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs
index 62519cbc50..d163eb56d1 100644
--- a/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs
+++ b/src/JsonApiDotNetCore/Serialization/Request/Adapters/ResourceIdentityAdapter.cs
@@ -46,6 +46,12 @@ private ResourceType ResolveType(IResourceIdentity identity, ResourceIdentityReq
         ResourceType? resourceType = _resourceGraph.FindResourceType(identity.Type);
 
         AssertIsKnownResourceType(resourceType, identity.Type, state);
+
+        if (state.Request.WriteOperation is WriteOperationKind.CreateResource or WriteOperationKind.UpdateResource)
+        {
+            AssertIsNotAbstractType(resourceType, identity.Type, state);
+        }
+
         AssertIsCompatibleResourceType(resourceType, requirements.ResourceType, requirements.RelationshipName, state);
 
         return resourceType;
@@ -67,6 +73,14 @@ private static void AssertIsKnownResourceType([NotNull] ResourceType? resourceTy
         }
     }
 
+    private static void AssertIsNotAbstractType(ResourceType resourceType, string typeName, RequestAdapterState state)
+    {
+        if (resourceType.ClrType.IsAbstract)
+        {
+            throw new ModelConversionException(state.Position, "Abstract resource type found.", $"Resource type '{typeName}' is abstract.");
+        }
+    }
+
     private static void AssertIsCompatibleResourceType(ResourceType actual, ResourceType? expected, string? relationshipName, RequestAdapterState state)
     {
         if (expected != null && !expected.ClrType.IsAssignableFrom(actual.ClrType))
diff --git a/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs b/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs
index 87046783c5..74733f6895 100644
--- a/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs
+++ b/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs
@@ -196,14 +196,17 @@ private async Task RetrieveResourceCountForNonPrimaryEndpointAsync(TId id, HasMa
         });
 
         ArgumentGuard.NotNull(resource, nameof(resource));
-        AssertPrimaryResourceTypeInJsonApiRequestIsNotNull(_request.PrimaryResourceType);
 
         using IDisposable _ = CodeTimingSessionManager.Current.Measure("Service - Create resource");
 
         TResource resourceFromRequest = resource;
         _resourceChangeTracker.SetRequestAttributeValues(resourceFromRequest);
 
-        TResource resourceForDatabase = await _repositoryAccessor.GetForCreateAsync<TResource, TId>(resource.Id, cancellationToken);
+        await RefreshResourceTypesInHierarchyToAssignInRelationshipsAsync(resourceFromRequest, cancellationToken);
+
+        Type resourceClrType = resourceFromRequest.GetClrType();
+        TResource resourceForDatabase = await _repositoryAccessor.GetForCreateAsync<TResource, TId>(resourceClrType, resourceFromRequest.Id, cancellationToken);
+        PromoteJsonApiRequest(resourceForDatabase);
 
         _resourceChangeTracker.SetInitiallyStoredAttributeValues(resourceForDatabase);
 
@@ -246,19 +249,44 @@ protected virtual async Task InitializeResourceAsync(TResource resourceForDataba
         await _resourceDefinitionAccessor.OnPrepareWriteAsync(resourceForDatabase, WriteOperationKind.CreateResource, cancellationToken);
     }
 
+    private async Task RefreshResourceTypesInHierarchyToAssignInRelationshipsAsync(TResource primaryResource, CancellationToken cancellationToken)
+    {
+        await ValidateResourcesToAssignInRelationshipsExistWithRefreshAsync(primaryResource, true, cancellationToken);
+    }
+
     protected async Task AssertResourcesToAssignInRelationshipsExistAsync(TResource primaryResource, CancellationToken cancellationToken)
+    {
+        await ValidateResourcesToAssignInRelationshipsExistWithRefreshAsync(primaryResource, false, cancellationToken);
+    }
+
+    private async Task ValidateResourcesToAssignInRelationshipsExistWithRefreshAsync(TResource primaryResource, bool onlyIfTypeHierarchy,
+        CancellationToken cancellationToken)
     {
         var missingResources = new List<MissingResourceInRelationship>();
 
         foreach ((QueryLayer queryLayer, RelationshipAttribute relationship) in _queryLayerComposer.ComposeForGetTargetedSecondaryResourceIds(primaryResource))
         {
-            object? rightValue = relationship.GetValue(primaryResource);
-            ICollection<IIdentifiable> rightResourceIds = _collectionConverter.ExtractResources(rightValue);
+            if (!onlyIfTypeHierarchy || relationship.RightType.IsPartOfTypeHierarchy())
+            {
+                object? rightValue = relationship.GetValue(primaryResource);
+                HashSet<IIdentifiable> rightResourceIds = _collectionConverter.ExtractResources(rightValue).ToHashSet(IdentifiableComparer.Instance);
+
+                if (rightResourceIds.Any())
+                {
+                    IAsyncEnumerable<MissingResourceInRelationship> missingResourcesInRelationship =
+                        GetMissingRightResourcesAsync(queryLayer, relationship, rightResourceIds, cancellationToken);
 
-            IAsyncEnumerable<MissingResourceInRelationship> missingResourcesInRelationship =
-                GetMissingRightResourcesAsync(queryLayer, relationship, rightResourceIds, cancellationToken);
+                    await missingResources.AddRangeAsync(missingResourcesInRelationship, cancellationToken);
 
-            await missingResources.AddRangeAsync(missingResourcesInRelationship, cancellationToken);
+                    // Some of the right-side resources from request may be typed as base types, but stored as derived types.
+                    // Now that we've fetched them, update the request types so that resource definitions observe the actually stored types.
+                    object? newRightValue = relationship is HasOneAttribute
+                        ? rightResourceIds.FirstOrDefault()
+                        : _collectionConverter.CopyToTypedCollection(rightResourceIds, relationship.Property.PropertyType);
+
+                    relationship.SetValue(primaryResource, newRightValue);
+                }
+            }
         }
 
         if (missingResources.Any())
@@ -268,20 +296,35 @@ protected async Task AssertResourcesToAssignInRelationshipsExistAsync(TResource
     }
 
     private async IAsyncEnumerable<MissingResourceInRelationship> GetMissingRightResourcesAsync(QueryLayer existingRightResourceIdsQueryLayer,
-        RelationshipAttribute relationship, ICollection<IIdentifiable> rightResourceIds, [EnumeratorCancellation] CancellationToken cancellationToken)
+        RelationshipAttribute relationship, ISet<IIdentifiable> rightResourceIds, [EnumeratorCancellation] CancellationToken cancellationToken)
     {
         IReadOnlyCollection<IIdentifiable> existingResources = await _repositoryAccessor.GetAsync(existingRightResourceIdsQueryLayer.ResourceType,
             existingRightResourceIdsQueryLayer, cancellationToken);
 
-        string[] existingResourceIds = existingResources.Select(resource => resource.StringId!).ToArray();
-
-        foreach (IIdentifiable rightResourceId in rightResourceIds)
+        foreach (IIdentifiable rightResourceId in rightResourceIds.ToArray())
         {
-            if (!existingResourceIds.Contains(rightResourceId.StringId))
+            Type rightResourceClrType = rightResourceId.GetClrType();
+            IIdentifiable? existingResourceId = existingResources.FirstOrDefault(resource => resource.StringId == rightResourceId.StringId);
+
+            if (existingResourceId != null)
             {
-                yield return new MissingResourceInRelationship(relationship.PublicName, existingRightResourceIdsQueryLayer.ResourceType.PublicName,
-                    rightResourceId.StringId!);
+                Type existingResourceClrType = existingResourceId.GetClrType();
+
+                if (rightResourceClrType.IsAssignableFrom(existingResourceClrType))
+                {
+                    if (rightResourceClrType != existingResourceClrType)
+                    {
+                        // PERF: As a side effect, we replace the resource base type from request with the derived type that is stored.
+                        rightResourceIds.Remove(rightResourceId);
+                        rightResourceIds.Add(existingResourceId);
+                    }
+
+                    continue;
+                }
             }
+
+            ResourceType requestResourceType = relationship.RightType.GetTypeOrDerived(rightResourceClrType);
+            yield return new MissingResourceInRelationship(relationship.PublicName, requestResourceType.PublicName, rightResourceId.StringId!);
         }
     }
 
@@ -292,6 +335,7 @@ public virtual async Task AddToToManyRelationshipAsync(TId leftId, string relati
         _traceWriter.LogMethodStart(new
         {
             leftId,
+            relationshipName,
             rightResourceIds
         });
 
@@ -302,36 +346,56 @@ public virtual async Task AddToToManyRelationshipAsync(TId leftId, string relati
 
         AssertHasRelationship(_request.Relationship, relationshipName);
 
+        TResource? resourceFromDatabase = null;
+
         if (rightResourceIds.Any() && _request.Relationship is HasManyAttribute { IsManyToMany: true } manyToManyRelationship)
         {
             // In the case of a many-to-many relationship, creating a duplicate entry in the join table results in a
             // unique constraint violation. We avoid that by excluding already-existing entries from the set in advance.
-            await RemoveExistingIdsFromRelationshipRightSideAsync(manyToManyRelationship, leftId, rightResourceIds, cancellationToken);
+            resourceFromDatabase = await RemoveExistingIdsFromRelationshipRightSideAsync(manyToManyRelationship, leftId, rightResourceIds, cancellationToken);
+        }
+
+        if (_request.Relationship.LeftType.IsPartOfTypeHierarchy())
+        {
+            // The left resource may be stored as a derived type. We fetch it, so we'll know the stored type, which
+            // enables to invoke IResourceDefinition<TResource> with TResource being the stored resource type.
+            resourceFromDatabase ??= await GetPrimaryResourceForUpdateAsync(leftId, cancellationToken);
+            PromoteJsonApiRequest(resourceFromDatabase);
+        }
+
+        ISet<IIdentifiable> effectiveRightResourceIds = rightResourceIds;
+
+        if (_request.Relationship.RightType.IsPartOfTypeHierarchy())
+        {
+            // Some of the incoming right-side resources may be stored as a derived type. We fetch them, so we'll know
+            // the stored types, which enables to invoke resource definitions with the stored right-side resources types.
+            object? rightValue = await AssertRightResourcesExistAsync(rightResourceIds, cancellationToken);
+            effectiveRightResourceIds = ((IEnumerable<IIdentifiable>)rightValue!).ToHashSet(IdentifiableComparer.Instance);
         }
 
         try
         {
-            await _repositoryAccessor.AddToToManyRelationshipAsync<TResource, TId>(leftId, rightResourceIds, cancellationToken);
+            await _repositoryAccessor.AddToToManyRelationshipAsync(resourceFromDatabase, leftId, effectiveRightResourceIds, cancellationToken);
         }
         catch (DataStoreUpdateException)
         {
             await GetPrimaryResourceByIdAsync(leftId, TopFieldSelection.OnlyIdAttribute, cancellationToken);
-            await AssertRightResourcesExistAsync(rightResourceIds, cancellationToken);
+            await AssertRightResourcesExistAsync(effectiveRightResourceIds, cancellationToken);
             throw;
         }
     }
 
-    private async Task RemoveExistingIdsFromRelationshipRightSideAsync(HasManyAttribute hasManyRelationship, TId leftId, ISet<IIdentifiable> rightResourceIds,
-        CancellationToken cancellationToken)
+    private async Task<TResource> RemoveExistingIdsFromRelationshipRightSideAsync(HasManyAttribute hasManyRelationship, TId leftId,
+        ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
     {
-        AssertRelationshipInJsonApiRequestIsNotNull(_request.Relationship);
-
         TResource leftResource = await GetForHasManyUpdateAsync(hasManyRelationship, leftId, rightResourceIds, cancellationToken);
 
-        object? rightValue = _request.Relationship.GetValue(leftResource);
+        object? rightValue = hasManyRelationship.GetValue(leftResource);
         ICollection<IIdentifiable> existingRightResourceIds = _collectionConverter.ExtractResources(rightValue);
 
         rightResourceIds.ExceptWith(existingRightResourceIds);
+
+        return leftResource;
     }
 
     private async Task<TResource> GetForHasManyUpdateAsync(HasManyAttribute hasManyRelationship, TId leftId, ISet<IIdentifiable> rightResourceIds,
@@ -344,11 +408,12 @@ private async Task<TResource> GetForHasManyUpdateAsync(HasManyAttribute hasManyR
         return leftResource;
     }
 
-    protected async Task AssertRightResourcesExistAsync(object? rightValue, CancellationToken cancellationToken)
+    protected async Task<object?> AssertRightResourcesExistAsync(object? rightValue, CancellationToken cancellationToken)
     {
         AssertRelationshipInJsonApiRequestIsNotNull(_request.Relationship);
 
-        ICollection<IIdentifiable> rightResourceIds = _collectionConverter.ExtractResources(rightValue);
+        HashSet<IIdentifiable> rightResourceIds = _collectionConverter.ExtractResources(rightValue).ToHashSet(IdentifiableComparer.Instance);
+        object? newRightValue = rightValue;
 
         if (rightResourceIds.Any())
         {
@@ -357,11 +422,19 @@ protected async Task AssertRightResourcesExistAsync(object? rightValue, Cancella
             List<MissingResourceInRelationship> missingResources =
                 await GetMissingRightResourcesAsync(queryLayer, _request.Relationship, rightResourceIds, cancellationToken).ToListAsync(cancellationToken);
 
+            // Some of the right-side resources from request may be typed as base types, but stored as derived types.
+            // Now that we've fetched them, update the request types so that resource definitions observe the actually stored types.
+            newRightValue = _request.Relationship is HasOneAttribute
+                ? rightResourceIds.FirstOrDefault()
+                : _collectionConverter.CopyToTypedCollection(rightResourceIds, _request.Relationship.Property.PropertyType);
+
             if (missingResources.Any())
             {
                 throw new ResourcesInRelationshipsNotFoundException(missingResources);
             }
         }
+
+        return newRightValue;
     }
 
     /// <inheritdoc />
@@ -380,7 +453,10 @@ protected async Task AssertRightResourcesExistAsync(object? rightValue, Cancella
         TResource resourceFromRequest = resource;
         _resourceChangeTracker.SetRequestAttributeValues(resourceFromRequest);
 
+        await RefreshResourceTypesInHierarchyToAssignInRelationshipsAsync(resourceFromRequest, cancellationToken);
+
         TResource resourceFromDatabase = await GetPrimaryResourceForUpdateAsync(id, cancellationToken);
+        PromoteJsonApiRequest(resourceFromDatabase);
 
         _resourceChangeTracker.SetInitiallyStoredAttributeValues(resourceFromDatabase);
 
@@ -420,17 +496,24 @@ public virtual async Task SetRelationshipAsync(TId leftId, string relationshipNa
 
         AssertHasRelationship(_request.Relationship, relationshipName);
 
+        object? effectiveRightValue = _request.Relationship.RightType.IsPartOfTypeHierarchy()
+            // Some of the incoming right-side resources may be stored as a derived type. We fetch them, so we'll know
+            // the stored types, which enables to invoke resource definitions with the stored right-side resources types.
+            ? await AssertRightResourcesExistAsync(rightValue, cancellationToken)
+            : rightValue;
+
         TResource resourceFromDatabase = await GetPrimaryResourceForUpdateAsync(leftId, cancellationToken);
+        PromoteJsonApiRequest(resourceFromDatabase);
 
         await _resourceDefinitionAccessor.OnPrepareWriteAsync(resourceFromDatabase, WriteOperationKind.SetRelationship, cancellationToken);
 
         try
         {
-            await _repositoryAccessor.SetRelationshipAsync(resourceFromDatabase, rightValue, cancellationToken);
+            await _repositoryAccessor.SetRelationshipAsync(resourceFromDatabase, effectiveRightValue, cancellationToken);
         }
         catch (DataStoreUpdateException)
         {
-            await AssertRightResourcesExistAsync(rightValue, cancellationToken);
+            await AssertRightResourcesExistAsync(effectiveRightValue, cancellationToken);
             throw;
         }
     }
@@ -445,9 +528,21 @@ public virtual async Task DeleteAsync(TId id, CancellationToken cancellationToke
 
         using IDisposable _ = CodeTimingSessionManager.Current.Measure("Repository - Delete resource");
 
+        AssertPrimaryResourceTypeInJsonApiRequestIsNotNull(_request.PrimaryResourceType);
+
+        TResource? resourceFromDatabase = null;
+
+        if (_request.PrimaryResourceType.IsPartOfTypeHierarchy())
+        {
+            // The resource to delete may be stored as a derived type. We fetch it, so we'll know the stored type, which
+            // enables to invoke IResourceDefinition<TResource> with TResource being the stored resource type.
+            resourceFromDatabase = await GetPrimaryResourceForUpdateAsync(id, cancellationToken);
+            PromoteJsonApiRequest(resourceFromDatabase);
+        }
+
         try
         {
-            await _repositoryAccessor.DeleteAsync<TResource, TId>(id, cancellationToken);
+            await _repositoryAccessor.DeleteAsync(resourceFromDatabase, id, cancellationToken);
         }
         catch (DataStoreUpdateException)
         {
@@ -476,10 +571,14 @@ public virtual async Task RemoveFromToManyRelationshipAsync(TId leftId, string r
         var hasManyRelationship = (HasManyAttribute)_request.Relationship;
 
         TResource resourceFromDatabase = await GetForHasManyUpdateAsync(hasManyRelationship, leftId, rightResourceIds, cancellationToken);
+        PromoteJsonApiRequest(resourceFromDatabase);
+
+        object? rightValue = await AssertRightResourcesExistAsync(rightResourceIds, cancellationToken);
+        ISet<IIdentifiable> effectiveRightResourceIds = ((IEnumerable<IIdentifiable>)rightValue!).ToHashSet(IdentifiableComparer.Instance);
 
-        await AssertRightResourcesExistAsync(rightResourceIds, cancellationToken);
+        await _resourceDefinitionAccessor.OnPrepareWriteAsync(resourceFromDatabase, WriteOperationKind.SetRelationship, cancellationToken);
 
-        await _repositoryAccessor.RemoveFromToManyRelationshipAsync(resourceFromDatabase, rightResourceIds, cancellationToken);
+        await _repositoryAccessor.RemoveFromToManyRelationshipAsync(resourceFromDatabase, effectiveRightResourceIds, cancellationToken);
     }
 
     protected async Task<TResource> GetPrimaryResourceByIdAsync(TId id, TopFieldSelection fieldSelection, CancellationToken cancellationToken)
@@ -511,6 +610,33 @@ protected async Task<TResource> GetPrimaryResourceForUpdateAsync(TId id, Cancell
         return resource;
     }
 
+    private void PromoteJsonApiRequest(TResource resourceFromDatabase)
+    {
+        // When using resource inheritance, the stored left-side resource may be more derived than what this endpoint assumes.
+        // In that case, we promote data in IJsonApiRequest to better represent what is going on.
+
+        Type storedType = resourceFromDatabase.GetClrType();
+
+        if (storedType != typeof(TResource))
+        {
+            AssertPrimaryResourceTypeInJsonApiRequestIsNotNull(_request.PrimaryResourceType);
+            ResourceType? derivedType = _request.PrimaryResourceType.GetAllConcreteDerivedTypes().FirstOrDefault(type => type.ClrType == storedType);
+
+            if (derivedType == null)
+            {
+                throw new InvalidConfigurationException($"Type '{storedType}' does not exist in the resource graph.");
+            }
+
+            var request = (JsonApiRequest)_request;
+            request.PrimaryResourceType = derivedType;
+
+            if (request.Relationship != null)
+            {
+                request.Relationship = derivedType.GetRelationshipByPublicName(request.Relationship.PublicName);
+            }
+        }
+    }
+
     [AssertionMethod]
     private void AssertPrimaryResourceExists([SysNotNull] TResource? resource)
     {
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Transactions/PerformerRepository.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Transactions/PerformerRepository.cs
index c50c52e08e..2302ac20f7 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Transactions/PerformerRepository.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Transactions/PerformerRepository.cs
@@ -19,7 +19,7 @@ public Task<int> CountAsync(FilterExpression? filter, CancellationToken cancella
         throw new NotImplementedException();
     }
 
-    public Task<Performer> GetForCreateAsync(int id, CancellationToken cancellationToken)
+    public Task<Performer> GetForCreateAsync(Type resourceClrType, int id, CancellationToken cancellationToken)
     {
         throw new NotImplementedException();
     }
@@ -39,7 +39,7 @@ public Task UpdateAsync(Performer resourceFromRequest, Performer resourceFromDat
         throw new NotImplementedException();
     }
 
-    public Task DeleteAsync(int id, CancellationToken cancellationToken)
+    public Task DeleteAsync(Performer? resourceFromDatabase, int id, CancellationToken cancellationToken)
     {
         throw new NotImplementedException();
     }
@@ -49,7 +49,7 @@ public Task SetRelationshipAsync(Performer leftResource, object? rightValue, Can
         throw new NotImplementedException();
     }
 
-    public Task AddToToManyRelationshipAsync(int leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
+    public Task AddToToManyRelationshipAsync(Performer? leftResource, int leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
     {
         throw new NotImplementedException();
     }
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/EagerLoading/BuildingRepository.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/EagerLoading/BuildingRepository.cs
index 572a7bd3e6..888f060ca1 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/EagerLoading/BuildingRepository.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/EagerLoading/BuildingRepository.cs
@@ -17,9 +17,9 @@ public BuildingRepository(ITargetedFields targetedFields, IDbContextResolver dbC
     {
     }
 
-    public override async Task<Building> GetForCreateAsync(int id, CancellationToken cancellationToken)
+    public override async Task<Building> GetForCreateAsync(Type resourceClrType, int id, CancellationToken cancellationToken)
     {
-        Building building = await base.GetForCreateAsync(id, cancellationToken);
+        Building building = await base.GetForCreateAsync(resourceClrType, id, cancellationToken);
 
         // Must ensure that an instance exists for this required relationship, so that POST Resource succeeds.
         building.PrimaryDoor = new Door
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/HitCountingResourceDefinition.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/HitCountingResourceDefinition.cs
index 57098822a1..8132728c90 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/HitCountingResourceDefinition.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/HitCountingResourceDefinition.cs
@@ -129,7 +129,7 @@ public override Task OnSetToManyRelationshipAsync(TResource leftResource, HasMan
         return base.OnSetToManyRelationshipAsync(leftResource, hasManyRelationship, rightResourceIds, writeOperation, cancellationToken);
     }
 
-    public override Task OnAddToRelationshipAsync(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+    public override Task OnAddToRelationshipAsync(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken)
     {
         if (ExtensibilityPointsToTrack.HasFlag(ResourceDefinitionExtensibilityPoints.OnAddToRelationshipAsync))
@@ -137,7 +137,7 @@ public override Task OnAddToRelationshipAsync(TId leftResourceId, HasManyAttribu
             _hitCounter.TrackInvocation<TResource>(ResourceDefinitionExtensibilityPoints.OnAddToRelationshipAsync);
         }
 
-        return base.OnAddToRelationshipAsync(leftResourceId, hasManyRelationship, rightResourceIds, cancellationToken);
+        return base.OnAddToRelationshipAsync(leftResource, hasManyRelationship, rightResourceIds, cancellationToken);
     }
 
     public override Task OnRemoveFromRelationshipAsync(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/FireAndForgetDelivery/FireForgetTests.Group.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/FireAndForgetDelivery/FireForgetTests.Group.cs
index e35efaeb52..5b4acbc311 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/FireAndForgetDelivery/FireForgetTests.Group.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/FireAndForgetDelivery/FireForgetTests.Group.cs
@@ -569,6 +569,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
 
         hitCounter.HitExtensibilityPoints.Should().BeEquivalentTo(new[]
         {
+            (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnPrepareWriteAsync),
             (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnRemoveFromRelationshipAsync),
             (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnWritingAsync),
             (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnWriteSucceededAsync)
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/MessagingGroupDefinition.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/MessagingGroupDefinition.cs
index ce8e10c62e..9365ff08a0 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/MessagingGroupDefinition.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/MessagingGroupDefinition.cs
@@ -80,10 +80,10 @@ public override async Task OnSetToManyRelationshipAsync(DomainGroup group, HasMa
         }
     }
 
-    public override async Task OnAddToRelationshipAsync(Guid groupId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+    public override async Task OnAddToRelationshipAsync(DomainGroup group, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken)
     {
-        await base.OnAddToRelationshipAsync(groupId, hasManyRelationship, rightResourceIds, cancellationToken);
+        await base.OnAddToRelationshipAsync(group, hasManyRelationship, rightResourceIds, cancellationToken);
 
         if (hasManyRelationship.Property.Name == nameof(DomainGroup.Users))
         {
@@ -98,11 +98,11 @@ public override async Task OnAddToRelationshipAsync(Guid groupId, HasManyAttribu
 
                 if (beforeUser.Group == null)
                 {
-                    content = new UserAddedToGroupContent(beforeUser.Id, groupId);
+                    content = new UserAddedToGroupContent(beforeUser.Id, group.Id);
                 }
-                else if (beforeUser.Group != null && beforeUser.Group.Id != groupId)
+                else if (beforeUser.Group != null && beforeUser.Group.Id != group.Id)
                 {
-                    content = new UserMovedToGroupContent(beforeUser.Id, beforeUser.Group.Id, groupId);
+                    content = new UserMovedToGroupContent(beforeUser.Id, beforeUser.Group.Id, group.Id);
                 }
 
                 if (content != null)
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/TransactionalOutboxPattern/OutboxTests.Group.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/TransactionalOutboxPattern/OutboxTests.Group.cs
index a5c61d1f70..16c4394ed8 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/TransactionalOutboxPattern/OutboxTests.Group.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/Microservices/TransactionalOutboxPattern/OutboxTests.Group.cs
@@ -606,6 +606,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
 
         hitCounter.HitExtensibilityPoints.Should().BeEquivalentTo(new[]
         {
+            (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnPrepareWriteAsync),
             (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnRemoveFromRelationshipAsync),
             (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnWritingAsync),
             (typeof(DomainGroup), ResourceDefinitionExtensibilityPoints.OnWriteSucceededAsync)
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ChangeTrackingDbContext.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ChangeTrackingDbContext.cs
new file mode 100644
index 0000000000..a335f493c4
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ChangeTrackingDbContext.cs
@@ -0,0 +1,16 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.ChangeTracking;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+public sealed class ChangeTrackingDbContext : ResourceInheritanceDbContext
+{
+    public DbSet<AlwaysMovingTandem> AlwaysMovingTandems => Set<AlwaysMovingTandem>();
+
+    public ChangeTrackingDbContext(DbContextOptions<ChangeTrackingDbContext> options)
+        : base(options)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ResourceInheritanceChangeTrackerTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ResourceInheritanceChangeTrackerTests.cs
new file mode 100644
index 0000000000..eb15e543c6
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ChangeTracking/ResourceInheritanceChangeTrackerTests.cs
@@ -0,0 +1,62 @@
+using System.Net;
+using FluentAssertions;
+using JsonApiDotNetCore.Serialization.Objects;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using TestBuildingBlocks;
+using Xunit;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.ChangeTracking;
+
+public sealed class ResourceInheritanceChangeTrackerTests
+    : IClassFixture<IntegrationTestContext<TestableStartup<ChangeTrackingDbContext>, ChangeTrackingDbContext>>
+{
+    private readonly IntegrationTestContext<TestableStartup<ChangeTrackingDbContext>, ChangeTrackingDbContext> _testContext;
+    private readonly ResourceInheritanceFakers _fakers = new();
+
+    public ResourceInheritanceChangeTrackerTests(IntegrationTestContext<TestableStartup<ChangeTrackingDbContext>, ChangeTrackingDbContext> testContext)
+    {
+        _testContext = testContext;
+
+        testContext.UseController<VehiclesController>();
+    }
+
+    [Fact]
+    public async Task Can_detect_side_effects_in_derived_type_at_abstract_endpoint()
+    {
+        // Arrange
+        AlwaysMovingTandem existingMovingTandem = _fakers.AlwaysMovingTandem.Generate();
+
+        int newGearCount = _fakers.AlwaysMovingTandem.Generate().GearCount;
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingMovingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "bikes",
+                id = existingMovingTandem.StringId,
+                attributes = new
+                {
+                    gearCount = newGearCount
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingMovingTandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.OK);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("alwaysMovingTandems");
+        responseDocument.Data.SingleValue.Attributes.ShouldContainKey("locationToken").With(value => value.Should().NotBe(existingMovingTandem.LocationToken));
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/AlwaysMovingTandem.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/AlwaysMovingTandem.cs
new file mode 100644
index 0000000000..5d5aa241e1
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/AlwaysMovingTandem.cs
@@ -0,0 +1,18 @@
+using System.ComponentModel.DataAnnotations.Schema;
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+
+[UsedImplicitly(ImplicitUseTargetFlags.Members)]
+[Resource(ControllerNamespace = "JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance")]
+public sealed class AlwaysMovingTandem : Bike
+{
+    [NotMapped]
+    [Attr]
+    public Guid LocationToken
+    {
+        get => Guid.NewGuid();
+        set => _ = value;
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs
index f18654b68c..112f8fe2a2 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/Models/VehicleManufacturer.cs
@@ -9,7 +9,7 @@ namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
 public sealed class VehicleManufacturer : Identifiable<long>
 {
     [Attr]
-    public string Name { get; set; } = null!;
+    public string? Name { get; set; }
 
     [HasMany]
     public ISet<Vehicle> Vehicles { get; set; } = new HashSet<Vehicle>();
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs
index 958304e6c7..23fa61b7ad 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceDbContext.cs
@@ -26,6 +26,12 @@ public abstract class ResourceInheritanceDbContext : DbContext
     public DbSet<StringProperty> StringProperties => Set<StringProperty>();
     public DbSet<NumberProperty> NumberProperties => Set<NumberProperty>();
 
+    public DbSet<VehicleManufacturer> VehicleManufacturers => Set<VehicleManufacturer>();
+    public DbSet<Box> Boxes => Set<Box>();
+    public DbSet<BicycleLight> BicycleLights => Set<BicycleLight>();
+    public DbSet<NavigationSystem> NavigationSystems => Set<NavigationSystem>();
+    public DbSet<GenericFeature> GenericFeatures => Set<GenericFeature>();
+
     protected ResourceInheritanceDbContext(DbContextOptions options)
         : base(options)
     {
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
index f0f74e5c1e..f455473627 100644
--- a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceFakers.cs
@@ -24,6 +24,13 @@ internal sealed class ResourceInheritanceFakers : FakerContainer
             .RuleFor(tandem => tandem.GearCount, faker => faker.Random.Int(1, 10))
             .RuleFor(tandem => tandem.PassengerCount, faker => faker.Random.Int(2, 150)));
 
+    private readonly Lazy<Faker<AlwaysMovingTandem>> _lazyAlwaysMovingTandemFaker = new(() =>
+        new Faker<AlwaysMovingTandem>()
+            .UseSeed(GetFakerSeed())
+            .RuleFor(movingTandem => movingTandem.Weight, faker => faker.Random.Decimal(10, 30))
+            .RuleFor(movingTandem => movingTandem.RequiresDriverLicense, _ => false)
+            .RuleFor(movingTandem => movingTandem.GearCount, faker => faker.Random.Int(1, 10)));
+
     private readonly Lazy<Faker<Car>> _lazyCarFaker = new(() =>
         new Faker<Car>()
             .UseSeed(GetFakerSeed())
@@ -122,6 +129,7 @@ internal sealed class ResourceInheritanceFakers : FakerContainer
 
     public Faker<Bike> Bike => _lazyBikeFaker.Value;
     public Faker<Tandem> Tandem => _lazyTandemFaker.Value;
+    public Faker<AlwaysMovingTandem> AlwaysMovingTandem => _lazyAlwaysMovingTandemFaker.Value;
     public Faker<Car> Car => _lazyCarFaker.Value;
     public Faker<Truck> Truck => _lazyTruckFaker.Value;
     public Faker<CarbonWheel> CarbonWheel => _lazyCarbonWheelFaker.Value;
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceWriteTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceWriteTests.cs
new file mode 100644
index 0000000000..f6c3dcfc22
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceInheritanceWriteTests.cs
@@ -0,0 +1,2741 @@
+using System.Net;
+using FluentAssertions;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Serialization.Objects;
+using JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.Models;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using TestBuildingBlocks;
+using Xunit;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
+
+public abstract class ResourceInheritanceWriteTests<TDbContext> : IClassFixture<IntegrationTestContext<TestableStartup<TDbContext>, TDbContext>>
+    where TDbContext : ResourceInheritanceDbContext
+{
+    private readonly IntegrationTestContext<TestableStartup<TDbContext>, TDbContext> _testContext;
+    private readonly ResourceInheritanceFakers _fakers = new();
+
+    protected ResourceInheritanceWriteTests(IntegrationTestContext<TestableStartup<TDbContext>, TDbContext> testContext)
+    {
+        _testContext = testContext;
+
+        testContext.UseController<VehiclesController>();
+        testContext.UseController<BikesController>();
+        testContext.UseController<TandemsController>();
+        testContext.UseController<MotorVehiclesController>();
+        testContext.UseController<CarsController>();
+        testContext.UseController<TrucksController>();
+
+        testContext.UseController<EnginesController>();
+        testContext.UseController<GasolineEnginesController>();
+        testContext.UseController<DieselEnginesController>();
+
+        testContext.UseController<WheelsController>();
+        testContext.UseController<ChromeWheelsController>();
+        testContext.UseController<CarbonWheelsController>();
+
+        testContext.UseController<VehicleManufacturersController>();
+
+        testContext.ConfigureServicesAfterStartup(services =>
+        {
+            services.AddSingleton<ResourceTypeCaptureStore<Bike, long>>();
+            services.AddResourceDefinition<ResourceTypeCapturingDefinition<Bike, long>>();
+
+            services.AddSingleton<ResourceTypeCaptureStore<Tandem, long>>();
+            services.AddResourceDefinition<ResourceTypeCapturingDefinition<Tandem, long>>();
+
+            services.AddSingleton<ResourceTypeCaptureStore<Car, long>>();
+            services.AddResourceDefinition<ResourceTypeCapturingDefinition<Car, long>>();
+
+            services.AddSingleton<ResourceTypeCaptureStore<CarbonWheel, long>>();
+            services.AddResourceDefinition<ResourceTypeCapturingDefinition<CarbonWheel, long>>();
+
+            services.AddSingleton<ResourceTypeCaptureStore<VehicleManufacturer, long>>();
+            services.AddResourceDefinition<ResourceTypeCapturingDefinition<VehicleManufacturer, long>>();
+        });
+
+        var bikeStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Bike, long>>();
+        bikeStore.Reset();
+
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+        tandemStore.Reset();
+
+        var carStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Car, long>>();
+        carStore.Reset();
+
+        var carbonWheelStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<CarbonWheel, long>>();
+        carbonWheelStore.Reset();
+
+        var manufacturerStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<VehicleManufacturer, long>>();
+        manufacturerStore.Reset();
+    }
+
+    [Fact]
+    public async Task Cannot_create_abstract_resource_at_abstract_endpoint()
+    {
+        // Arrange
+        Tandem newTandem = _fakers.Tandem.Generate();
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicles",
+                attributes = new
+                {
+                    weight = newTandem.Weight
+                }
+            }
+        };
+
+        const string route = "/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.UnprocessableEntity);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.UnprocessableEntity);
+        error.Title.Should().Be("Failed to deserialize request body: Abstract resource type found.");
+        error.Detail.Should().Be("Resource type 'vehicles' is abstract.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data/type");
+    }
+
+    [Fact]
+    public async Task Can_create_concrete_base_resource_at_abstract_endpoint_with_relationships()
+    {
+        // Arrange
+        var bikeStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Bike, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+        Box existingBox = _fakers.Box.Generate();
+        BicycleLight existingLight = _fakers.BicycleLight.Generate();
+
+        Bike newBike = _fakers.Bike.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Wheels.Add(existingChromeWheel);
+            dbContext.Boxes.Add(existingBox);
+            dbContext.BicycleLights.Add(existingLight);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "bikes",
+                attributes = new
+                {
+                    weight = newBike.Weight,
+                    requiresDriverLicense = newBike.RequiresDriverLicense,
+                    gearCount = newBike.GearCount
+                },
+                relationships = new
+                {
+                    manufacturer = new
+                    {
+                        data = new
+                        {
+                            type = "vehicleManufacturers",
+                            id = existingManufacturer.StringId
+                        }
+                    },
+                    wheels = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "chromeWheels",
+                                id = existingChromeWheel.StringId
+                            }
+                        }
+                    },
+                    cargoBox = new
+                    {
+                        data = new
+                        {
+                            type = "boxes",
+                            id = existingBox.StringId
+                        }
+                    },
+                    lights = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "bicycleLights",
+                                id = existingLight.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("bikes");
+        responseDocument.Data.SingleValue.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "gearCount");
+        responseDocument.Data.SingleValue.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights");
+
+        long newBikeId = long.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            // @formatter:wrap_chained_method_calls chop_always
+            // @formatter:keep_existing_linebreaks true
+
+            Bike bikeInDatabase = await dbContext.Bikes
+                .Include(tandem => tandem.Manufacturer)
+                .Include(tandem => tandem.Wheels)
+                .Include(tandem => tandem.CargoBox)
+                .Include(tandem => tandem.Lights)
+                .FirstWithIdAsync(newBikeId);
+
+            // @formatter:keep_existing_linebreaks restore
+            // @formatter:wrap_chained_method_calls restore
+
+            bikeInDatabase.Should().BeOfType<Bike>();
+            bikeInDatabase.Weight.Should().Be(newBike.Weight);
+            bikeInDatabase.RequiresDriverLicense.Should().Be(newBike.RequiresDriverLicense);
+            bikeInDatabase.GearCount.Should().Be(newBike.GearCount);
+
+            bikeInDatabase.Manufacturer.ShouldNotBeNull();
+            bikeInDatabase.Manufacturer.Id.Should().Be(existingManufacturer.Id);
+
+            bikeInDatabase.Wheels.ShouldHaveCount(1);
+            bikeInDatabase.Wheels.ElementAt(0).Should().BeOfType<ChromeWheel>();
+            bikeInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingChromeWheel.Id);
+
+            bikeInDatabase.CargoBox.ShouldNotBeNull();
+            bikeInDatabase.CargoBox.Id.Should().Be(existingBox.Id);
+
+            bikeInDatabase.Lights.ShouldHaveCount(1);
+            bikeInDatabase.Lights.ElementAt(0).Id.Should().Be(existingLight.Id);
+        });
+
+        bikeStore.AssertLeftType<Bike>();
+        bikeStore.AssertRightTypes(typeof(VehicleManufacturer), typeof(ChromeWheel), typeof(Box), typeof(BicycleLight));
+    }
+
+    [Fact]
+    public async Task Can_create_concrete_derived_resource_at_abstract_endpoint_with_relationships()
+    {
+        // Arrange
+        var carStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Car, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+        CarbonWheel existingCarbonWheel = _fakers.CarbonWheel.Generate();
+        GasolineEngine existingGasolineEngine = _fakers.GasolineEngine.Generate();
+        NavigationSystem existingNavigationSystem = _fakers.NavigationSystem.Generate();
+        GenericFeature existingFeature = _fakers.GenericFeature.Generate();
+
+        Car newCar = _fakers.Car.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Wheels.Add(existingCarbonWheel);
+            dbContext.Engines.Add(existingGasolineEngine);
+            dbContext.NavigationSystems.Add(existingNavigationSystem);
+            dbContext.GenericFeatures.Add(existingFeature);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "cars",
+                attributes = new
+                {
+                    weight = newCar.Weight,
+                    requiresDriverLicense = newCar.RequiresDriverLicense,
+                    licensePlate = newCar.LicensePlate,
+                    seatCount = newCar.SeatCount
+                },
+                relationships = new
+                {
+                    manufacturer = new
+                    {
+                        data = new
+                        {
+                            type = "vehicleManufacturers",
+                            id = existingManufacturer.StringId
+                        }
+                    },
+                    wheels = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "carbonWheels",
+                                id = existingCarbonWheel.StringId
+                            }
+                        }
+                    },
+                    engine = new
+                    {
+                        data = new
+                        {
+                            type = "gasolineEngines",
+                            id = existingGasolineEngine.StringId
+                        }
+                    },
+                    navigationSystem = new
+                    {
+                        data = new
+                        {
+                            type = "navigationSystems",
+                            id = existingNavigationSystem.StringId
+                        }
+                    },
+                    features = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "genericFeatures",
+                                id = existingFeature.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("cars");
+        responseDocument.Data.SingleValue.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "licensePlate", "seatCount");
+        responseDocument.Data.SingleValue.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "engine", "navigationSystem", "features");
+
+        long newCarId = long.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            // @formatter:wrap_chained_method_calls chop_always
+            // @formatter:keep_existing_linebreaks true
+
+            Car carInDatabase = await dbContext.Cars
+                .Include(car => car.Manufacturer)
+                .Include(car => car.Wheels)
+                .Include(car => car.Engine)
+                .Include(car => car.NavigationSystem)
+                .Include(car => car.Features)
+                .FirstWithIdAsync(newCarId);
+
+            // @formatter:keep_existing_linebreaks restore
+            // @formatter:wrap_chained_method_calls restore
+
+            carInDatabase.Should().BeOfType<Car>();
+            carInDatabase.Weight.Should().Be(newCar.Weight);
+            carInDatabase.RequiresDriverLicense.Should().Be(newCar.RequiresDriverLicense);
+            carInDatabase.LicensePlate.Should().Be(newCar.LicensePlate);
+            carInDatabase.SeatCount.Should().Be(newCar.SeatCount);
+
+            carInDatabase.Manufacturer.ShouldNotBeNull();
+            carInDatabase.Manufacturer.Id.Should().Be(existingManufacturer.Id);
+
+            carInDatabase.Wheels.ShouldHaveCount(1);
+            carInDatabase.Wheels.ElementAt(0).Should().BeOfType<CarbonWheel>();
+            carInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingCarbonWheel.Id);
+
+            carInDatabase.Engine.ShouldNotBeNull();
+            carInDatabase.Engine.Should().BeOfType<GasolineEngine>();
+            carInDatabase.Engine.Id.Should().Be(existingGasolineEngine.Id);
+
+            carInDatabase.NavigationSystem.ShouldNotBeNull();
+            carInDatabase.NavigationSystem.Id.Should().Be(existingNavigationSystem.Id);
+
+            carInDatabase.Features.ShouldHaveCount(1);
+            carInDatabase.Features.ElementAt(0).Id.Should().Be(existingFeature.Id);
+        });
+
+        carStore.AssertLeftType<Car>();
+        carStore.AssertRightTypes(typeof(VehicleManufacturer), typeof(CarbonWheel), typeof(GasolineEngine), typeof(NavigationSystem), typeof(GenericFeature));
+    }
+
+    [Fact]
+    public async Task Can_create_concrete_derived_resource_at_concrete_base_endpoint_with_relationships()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+        Box existingBox = _fakers.Box.Generate();
+        BicycleLight existingLight = _fakers.BicycleLight.Generate();
+        GenericFeature existingFeature = _fakers.GenericFeature.Generate();
+
+        Tandem newTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Wheels.Add(existingChromeWheel);
+            dbContext.Boxes.Add(existingBox);
+            dbContext.BicycleLights.Add(existingLight);
+            dbContext.GenericFeatures.Add(existingFeature);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "tandems",
+                attributes = new
+                {
+                    weight = newTandem.Weight,
+                    requiresDriverLicense = newTandem.RequiresDriverLicense,
+                    gearCount = newTandem.GearCount,
+                    passengerCount = newTandem.PassengerCount
+                },
+                relationships = new
+                {
+                    manufacturer = new
+                    {
+                        data = new
+                        {
+                            type = "vehicleManufacturers",
+                            id = existingManufacturer.StringId
+                        }
+                    },
+                    wheels = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "chromeWheels",
+                                id = existingChromeWheel.StringId
+                            }
+                        }
+                    },
+                    cargoBox = new
+                    {
+                        data = new
+                        {
+                            type = "boxes",
+                            id = existingBox.StringId
+                        }
+                    },
+                    lights = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "bicycleLights",
+                                id = existingLight.StringId
+                            }
+                        }
+                    },
+                    features = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "genericFeatures",
+                                id = existingFeature.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/bikes";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("tandems");
+        responseDocument.Data.SingleValue.Attributes.ShouldOnlyContainKeys("weight", "requiresDriverLicense", "gearCount", "passengerCount");
+        responseDocument.Data.SingleValue.Relationships.ShouldOnlyContainKeys("manufacturer", "wheels", "cargoBox", "lights", "features");
+
+        long newTandemId = long.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            // @formatter:wrap_chained_method_calls chop_always
+            // @formatter:keep_existing_linebreaks true
+
+            Tandem tandemInDatabase = await dbContext.Tandems
+                .Include(tandem => tandem.Manufacturer)
+                .Include(tandem => tandem.Wheels)
+                .Include(tandem => tandem.CargoBox)
+                .Include(tandem => tandem.Lights)
+                .Include(tandem => tandem.Features)
+                .FirstWithIdAsync(newTandemId);
+
+            // @formatter:keep_existing_linebreaks restore
+            // @formatter:wrap_chained_method_calls restore
+
+            tandemInDatabase.Should().BeOfType<Tandem>();
+            tandemInDatabase.Weight.Should().Be(newTandem.Weight);
+            tandemInDatabase.RequiresDriverLicense.Should().Be(newTandem.RequiresDriverLicense);
+            tandemInDatabase.GearCount.Should().Be(newTandem.GearCount);
+            tandemInDatabase.PassengerCount.Should().Be(newTandem.PassengerCount);
+
+            tandemInDatabase.Manufacturer.ShouldNotBeNull();
+            tandemInDatabase.Manufacturer.Id.Should().Be(existingManufacturer.Id);
+
+            tandemInDatabase.Wheels.ShouldHaveCount(1);
+            tandemInDatabase.Wheels.ElementAt(0).Should().BeOfType<ChromeWheel>();
+            tandemInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingChromeWheel.Id);
+
+            tandemInDatabase.CargoBox.ShouldNotBeNull();
+            tandemInDatabase.CargoBox.Id.Should().Be(existingBox.Id);
+
+            tandemInDatabase.Lights.ShouldHaveCount(1);
+            tandemInDatabase.Lights.ElementAt(0).Id.Should().Be(existingLight.Id);
+
+            tandemInDatabase.Features.ShouldHaveCount(1);
+            tandemInDatabase.Features.ElementAt(0).Id.Should().Be(existingFeature.Id);
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(typeof(VehicleManufacturer), typeof(ChromeWheel), typeof(Box), typeof(BicycleLight), typeof(GenericFeature));
+    }
+
+    [Fact]
+    public async Task Cannot_create_concrete_base_resource_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Bike newBike = _fakers.Bike.Generate();
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "bikes",
+                attributes = new
+                {
+                    weight = newBike.Weight,
+                    requiresDriverLicense = newBike.RequiresDriverLicense,
+                    gearCount = newBike.GearCount
+                }
+            }
+        };
+
+        const string route = "/tandems";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Conflict);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.Conflict);
+        error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
+        error.Detail.Should().Be("Type 'bikes' is not convertible to type 'tandems'.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data/type");
+    }
+
+    [Fact]
+    public async Task Cannot_create_resource_with_abstract_relationship_type()
+    {
+        // Arrange
+        DieselEngine existingEngine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Engines.Add(existingEngine);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "trucks",
+                relationships = new
+                {
+                    engine = new
+                    {
+                        data = new
+                        {
+                            type = "engines",
+                            id = existingEngine.StringId
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/trucks";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.UnprocessableEntity);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.UnprocessableEntity);
+        error.Title.Should().Be("Failed to deserialize request body: Abstract resource type found.");
+        error.Detail.Should().Be("Resource type 'engines' is abstract.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data/relationships/engine/data/type");
+    }
+
+    [Fact]
+    public async Task Can_create_resource_with_concrete_base_relationship_type_stored_as_derived_type()
+    {
+        // Arrange
+        var carbonWheelStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<CarbonWheel, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "carbonWheels",
+                relationships = new
+                {
+                    vehicle = new
+                    {
+                        data = new
+                        {
+                            type = "bikes",
+                            id = existingTandem.StringId
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/carbonWheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("carbonWheels");
+        responseDocument.Data.SingleValue.Attributes.ShouldNotBeEmpty();
+        responseDocument.Data.SingleValue.Relationships.ShouldNotBeEmpty();
+
+        long newCarbonWheelId = long.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            CarbonWheel carbonWheelInDatabase = await dbContext.CarbonWheels.Include(wheel => wheel.Vehicle).FirstWithIdAsync(newCarbonWheelId);
+
+            carbonWheelInDatabase.Should().BeOfType<CarbonWheel>();
+            carbonWheelInDatabase.Vehicle.ShouldNotBeNull();
+            carbonWheelInDatabase.Vehicle.Should().BeOfType<Tandem>();
+            carbonWheelInDatabase.Vehicle.Id.Should().Be(existingTandem.Id);
+        });
+
+        carbonWheelStore.AssertLeftType<CarbonWheel>();
+        carbonWheelStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Can_create_resource_with_concrete_base_ToOne_relationship_type_stored_as_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        var carbonWheelStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<CarbonWheel, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "carbonWheels",
+                relationships = new
+                {
+                    vehicle = new
+                    {
+                        data = new
+                        {
+                            type = "bikes",
+                            id = existingTandem.StringId
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/carbonWheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("carbonWheels");
+        responseDocument.Data.SingleValue.Attributes.ShouldNotBeEmpty();
+        responseDocument.Data.SingleValue.Relationships.ShouldNotBeEmpty();
+
+        long newCarbonWheelId = long.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            CarbonWheel carbonWheelInDatabase = await dbContext.CarbonWheels.Include(wheel => wheel.Vehicle).FirstWithIdAsync(newCarbonWheelId);
+
+            carbonWheelInDatabase.Should().BeOfType<CarbonWheel>();
+            carbonWheelInDatabase.Vehicle.ShouldNotBeNull();
+            carbonWheelInDatabase.Vehicle.Should().BeOfType<Tandem>();
+            carbonWheelInDatabase.Vehicle.Id.Should().Be(existingTandem.Id);
+        });
+
+        carbonWheelStore.AssertLeftType<CarbonWheel>();
+        carbonWheelStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Can_create_resource_with_concrete_base_ToMany_relationship_type_stored_as_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        var manufacturerStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<VehicleManufacturer, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicleManufacturers",
+                relationships = new
+                {
+                    vehicles = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "bikes",
+                                id = existingTandem.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/vehicleManufacturers";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Created);
+
+        responseDocument.Data.SingleValue.ShouldNotBeNull();
+        responseDocument.Data.SingleValue.Type.Should().Be("vehicleManufacturers");
+        responseDocument.Data.SingleValue.Attributes.ShouldNotBeEmpty();
+        responseDocument.Data.SingleValue.Relationships.ShouldNotBeEmpty();
+
+        long newManufacturerId = long.Parse(responseDocument.Data.SingleValue.Id.ShouldNotBeNull());
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            VehicleManufacturer manufacturerInDatabase = await dbContext.VehicleManufacturers.Include(manufacturer => manufacturer.Vehicles)
+                .FirstWithIdAsync(newManufacturerId);
+
+            manufacturerInDatabase.Vehicles.ShouldHaveCount(1);
+            manufacturerInDatabase.Vehicles.ElementAt(0).Should().BeOfType<Tandem>();
+            manufacturerInDatabase.Vehicles.ElementAt(0).Id.Should().Be(existingTandem.Id);
+        });
+
+        manufacturerStore.AssertLeftType<VehicleManufacturer>();
+        manufacturerStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Cannot_create_resource_with_concrete_derived_ToOne_relationship_type_stored_as_sibling_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "carbonWheels",
+                relationships = new
+                {
+                    vehicle = new
+                    {
+                        data = new
+                        {
+                            type = "trucks",
+                            id = existingTandem.StringId
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{existingTandem.StringId}' in relationship 'vehicle' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_create_resource_with_concrete_derived_ToMany_relationship_type_stored_as_sibling_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        Truck existingTruck = _fakers.Truck.Generate();
+        existingTruck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTruck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicleManufacturers",
+                relationships = new
+                {
+                    vehicles = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "cars",
+                                id = existingTruck.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/vehicleManufacturers";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'cars' with ID '{existingTruck.StringId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_create_resource_with_unknown_resource_in_ToOne_relationship_at_resource_endpoint()
+    {
+        // Arrange
+        string unknownTruckId = Unknown.StringId.For<Truck, long>();
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "carbonWheels",
+                relationships = new
+                {
+                    vehicle = new
+                    {
+                        data = new
+                        {
+                            type = "trucks",
+                            id = unknownTruckId
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{unknownTruckId}' in relationship 'vehicle' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_create_resource_with_unknown_resources_in_ToMany_relationship_at_resource_endpoint()
+    {
+        // Arrange
+        string unknownTruckId = Unknown.StringId.For<Truck, long>();
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicleManufacturers",
+                relationships = new
+                {
+                    vehicles = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "trucks",
+                                id = unknownTruckId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        const string route = "/vehicleManufacturers";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{unknownTruckId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_update_abstract_resource_at_abstract_endpoint()
+    {
+        // Arrange
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        int newPassengerCount = _fakers.Tandem.Generate().PassengerCount;
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicles",
+                id = existingTandem.StringId,
+                attributes = new
+                {
+                    passengerCount = newPassengerCount
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingTandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.UnprocessableEntity);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.UnprocessableEntity);
+        error.Title.Should().Be("Failed to deserialize request body: Abstract resource type found.");
+        error.Detail.Should().Be("Resource type 'vehicles' is abstract.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data/type");
+    }
+
+    [Fact]
+    public async Task Can_update_concrete_base_resource_at_abstract_endpoint_with_relationships()
+    {
+        // Arrange
+        var bikeStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Bike, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+        Box existingBox = _fakers.Box.Generate();
+        BicycleLight existingLight = _fakers.BicycleLight.Generate();
+
+        Bike existingBike = _fakers.Bike.Generate();
+        Bike newBike = _fakers.Bike.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Wheels.Add(existingChromeWheel);
+            dbContext.Boxes.Add(existingBox);
+            dbContext.BicycleLights.Add(existingLight);
+            dbContext.Vehicles.Add(existingBike);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "bikes",
+                id = existingBike.StringId,
+                attributes = new
+                {
+                    weight = newBike.Weight,
+                    requiresDriverLicense = newBike.RequiresDriverLicense,
+                    gearCount = newBike.GearCount
+                },
+                relationships = new
+                {
+                    manufacturer = new
+                    {
+                        data = new
+                        {
+                            type = "vehicleManufacturers",
+                            id = existingManufacturer.StringId
+                        }
+                    },
+                    wheels = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "chromeWheels",
+                                id = existingChromeWheel.StringId
+                            }
+                        }
+                    },
+                    cargoBox = new
+                    {
+                        data = new
+                        {
+                            type = "boxes",
+                            id = existingBox.StringId
+                        }
+                    },
+                    lights = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "bicycleLights",
+                                id = existingLight.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingBike.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            // @formatter:wrap_chained_method_calls chop_always
+            // @formatter:keep_existing_linebreaks true
+
+            Bike bikeInDatabase = await dbContext.Bikes
+                .Include(tandem => tandem.Manufacturer)
+                .Include(tandem => tandem.Wheels)
+                .Include(tandem => tandem.CargoBox)
+                .Include(tandem => tandem.Lights)
+                .FirstWithIdAsync(existingBike.Id);
+
+            // @formatter:keep_existing_linebreaks restore
+            // @formatter:wrap_chained_method_calls restore
+
+            bikeInDatabase.Should().BeOfType<Bike>();
+            bikeInDatabase.Weight.Should().Be(newBike.Weight);
+            bikeInDatabase.RequiresDriverLicense.Should().Be(newBike.RequiresDriverLicense);
+            bikeInDatabase.GearCount.Should().Be(newBike.GearCount);
+
+            bikeInDatabase.Manufacturer.ShouldNotBeNull();
+            bikeInDatabase.Manufacturer.Id.Should().Be(existingManufacturer.Id);
+
+            bikeInDatabase.Wheels.ShouldHaveCount(1);
+            bikeInDatabase.Wheels.ElementAt(0).Should().BeOfType<ChromeWheel>();
+            bikeInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingChromeWheel.Id);
+
+            bikeInDatabase.CargoBox.ShouldNotBeNull();
+            bikeInDatabase.CargoBox.Id.Should().Be(existingBox.Id);
+
+            bikeInDatabase.Lights.ShouldHaveCount(1);
+            bikeInDatabase.Lights.ElementAt(0).Id.Should().Be(existingLight.Id);
+        });
+
+        bikeStore.AssertLeftType<Bike>();
+        bikeStore.AssertRightTypes(typeof(VehicleManufacturer), typeof(ChromeWheel), typeof(Box), typeof(BicycleLight));
+    }
+
+    [Fact]
+    public async Task Can_update_concrete_base_resource_stored_as_concrete_derived_at_abstract_endpoint_with_relationships()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+        Box existingBox = _fakers.Box.Generate();
+        BicycleLight existingLight = _fakers.BicycleLight.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+        Bike newBike = _fakers.Bike.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Wheels.Add(existingChromeWheel);
+            dbContext.Boxes.Add(existingBox);
+            dbContext.BicycleLights.Add(existingLight);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "bikes",
+                id = existingTandem.StringId,
+                attributes = new
+                {
+                    weight = newBike.Weight,
+                    requiresDriverLicense = newBike.RequiresDriverLicense,
+                    gearCount = newBike.GearCount
+                },
+                relationships = new
+                {
+                    manufacturer = new
+                    {
+                        data = new
+                        {
+                            type = "vehicleManufacturers",
+                            id = existingManufacturer.StringId
+                        }
+                    },
+                    wheels = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "chromeWheels",
+                                id = existingChromeWheel.StringId
+                            }
+                        }
+                    },
+                    cargoBox = new
+                    {
+                        data = new
+                        {
+                            type = "boxes",
+                            id = existingBox.StringId
+                        }
+                    },
+                    lights = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "bicycleLights",
+                                id = existingLight.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingTandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            // @formatter:wrap_chained_method_calls chop_always
+            // @formatter:keep_existing_linebreaks true
+
+            Tandem tandemInDatabase = await dbContext.Tandems
+                .Include(tandem => tandem.Manufacturer)
+                .Include(tandem => tandem.Wheels)
+                .Include(tandem => tandem.CargoBox)
+                .Include(tandem => tandem.Lights)
+                .FirstWithIdAsync(existingTandem.Id);
+
+            // @formatter:keep_existing_linebreaks restore
+            // @formatter:wrap_chained_method_calls restore
+
+            tandemInDatabase.Should().BeOfType<Tandem>();
+            tandemInDatabase.Weight.Should().Be(newBike.Weight);
+            tandemInDatabase.RequiresDriverLicense.Should().Be(newBike.RequiresDriverLicense);
+            tandemInDatabase.GearCount.Should().Be(newBike.GearCount);
+
+            tandemInDatabase.Manufacturer.ShouldNotBeNull();
+            tandemInDatabase.Manufacturer.Id.Should().Be(existingManufacturer.Id);
+
+            tandemInDatabase.Wheels.ShouldHaveCount(1);
+            tandemInDatabase.Wheels.ElementAt(0).Should().BeOfType<ChromeWheel>();
+            tandemInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingChromeWheel.Id);
+
+            tandemInDatabase.CargoBox.ShouldNotBeNull();
+            tandemInDatabase.CargoBox.Id.Should().Be(existingBox.Id);
+
+            tandemInDatabase.Lights.ShouldHaveCount(1);
+            tandemInDatabase.Lights.ElementAt(0).Id.Should().Be(existingLight.Id);
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(typeof(VehicleManufacturer), typeof(ChromeWheel), typeof(Box), typeof(BicycleLight));
+    }
+
+    [Fact]
+    public async Task Cannot_update_concrete_base_resource_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        int newPassengerCount = _fakers.Tandem.Generate().PassengerCount;
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "bikes",
+                id = existingTandem.StringId,
+                attributes = new
+                {
+                    passengerCount = newPassengerCount
+                }
+            }
+        };
+
+        string route = $"/tandems/{existingTandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.Conflict);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.Conflict);
+        error.Title.Should().Be("Failed to deserialize request body: Incompatible resource type found.");
+        error.Detail.Should().Be("Type 'bikes' is not convertible to type 'tandems'.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data/type");
+    }
+
+    [Fact]
+    public async Task Cannot_update_resource_with_abstract_relationship_type()
+    {
+        // Arrange
+        Truck existingTruck = _fakers.Truck.Generate();
+        existingTruck.Engine = _fakers.GasolineEngine.Generate();
+
+        DieselEngine existingEngine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTruck);
+            dbContext.Engines.Add(existingEngine);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "trucks",
+                id = existingTruck.StringId,
+                relationships = new
+                {
+                    engine = new
+                    {
+                        data = new
+                        {
+                            type = "engines",
+                            id = existingEngine.StringId
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/trucks/{existingTruck.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.UnprocessableEntity);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.UnprocessableEntity);
+        error.Title.Should().Be("Failed to deserialize request body: Abstract resource type found.");
+        error.Detail.Should().Be("Resource type 'engines' is abstract.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data/relationships/engine/data/type");
+    }
+
+    [Fact]
+    public async Task Can_update_resource_with_concrete_base_ToOne_relationship_type_stored_as_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        var carbonWheelStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<CarbonWheel, long>>();
+
+        CarbonWheel existingCarbonWheel = _fakers.CarbonWheel.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Wheels.Add(existingCarbonWheel);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "carbonWheels",
+                id = existingCarbonWheel.StringId,
+                relationships = new
+                {
+                    vehicle = new
+                    {
+                        data = new
+                        {
+                            type = "bikes",
+                            id = existingTandem.StringId
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/carbonWheels/{existingCarbonWheel.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            CarbonWheel carbonWheelInDatabase = await dbContext.CarbonWheels.Include(wheel => wheel.Vehicle).FirstWithIdAsync(existingCarbonWheel.Id);
+
+            carbonWheelInDatabase.Should().BeOfType<CarbonWheel>();
+            carbonWheelInDatabase.Vehicle.ShouldNotBeNull();
+            carbonWheelInDatabase.Vehicle.Should().BeOfType<Tandem>();
+            carbonWheelInDatabase.Vehicle.Id.Should().Be(existingTandem.Id);
+        });
+
+        carbonWheelStore.AssertLeftType<CarbonWheel>();
+        carbonWheelStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Can_update_resource_with_concrete_base_ToMany_relationship_type_stored_as_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        var manufacturerStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<VehicleManufacturer, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicleManufacturers",
+                id = existingManufacturer.StringId,
+                relationships = new
+                {
+                    vehicles = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "bikes",
+                                id = existingTandem.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            VehicleManufacturer manufacturerInDatabase = await dbContext.VehicleManufacturers.Include(manufacturer => manufacturer.Vehicles)
+                .FirstWithIdAsync(existingManufacturer.Id);
+
+            manufacturerInDatabase.Vehicles.ShouldHaveCount(1);
+            manufacturerInDatabase.Vehicles.ElementAt(0).Should().BeOfType<Tandem>();
+            manufacturerInDatabase.Vehicles.ElementAt(0).Id.Should().Be(existingTandem.Id);
+        });
+
+        manufacturerStore.AssertLeftType<VehicleManufacturer>();
+        manufacturerStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Cannot_update_resource_with_concrete_derived_ToOne_relationship_type_stored_as_sibling_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        CarbonWheel existingCarbonWheel = _fakers.CarbonWheel.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Wheels.Add(existingCarbonWheel);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "carbonWheels",
+                id = existingCarbonWheel.StringId,
+                relationships = new
+                {
+                    vehicle = new
+                    {
+                        data = new
+                        {
+                            type = "trucks",
+                            id = existingTandem.StringId
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/wheels/{existingCarbonWheel.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{existingTandem.StringId}' in relationship 'vehicle' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_update_resource_with_concrete_derived_ToMany_relationship_type_stored_as_sibling_derived_type_at_resource_endpoint()
+    {
+        // Arrange
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        Truck existingTruck = _fakers.Truck.Generate();
+        existingTruck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Vehicles.Add(existingTruck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicleManufacturers",
+                id = existingManufacturer.StringId,
+                relationships = new
+                {
+                    vehicles = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "cars",
+                                id = existingTruck.StringId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'cars' with ID '{existingTruck.StringId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_update_resource_with_unknown_resource_in_ToOne_relationship_at_resource_endpoint()
+    {
+        // Arrange
+        CarbonWheel existingCarbonWheel = _fakers.CarbonWheel.Generate();
+
+        string unknownTruckId = Unknown.StringId.For<Truck, long>();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Wheels.Add(existingCarbonWheel);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "carbonWheels",
+                id = existingCarbonWheel.StringId,
+                relationships = new
+                {
+                    vehicle = new
+                    {
+                        data = new
+                        {
+                            type = "trucks",
+                            id = unknownTruckId
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/wheels/{existingCarbonWheel.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{unknownTruckId}' in relationship 'vehicle' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_update_resource_with_unknown_resources_in_ToMany_relationship_at_resource_endpoint()
+    {
+        // Arrange
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        string unknownTruckId = Unknown.StringId.For<Truck, long>();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicleManufacturers",
+                id = existingManufacturer.StringId,
+                relationships = new
+                {
+                    vehicles = new
+                    {
+                        data = new[]
+                        {
+                            new
+                            {
+                                type = "trucks",
+                                id = unknownTruckId
+                            }
+                        }
+                    }
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{unknownTruckId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_delete_resource_stored_as_concrete_derived_at_abstract_endpoint()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/vehicles/{existingTandem.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecuteDeleteAsync<string>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Tandem? tandemInDatabase = await dbContext.Tandems.FirstWithIdOrDefaultAsync(existingTandem.Id);
+
+            tandemInDatabase.Should().BeNull();
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(Array.Empty<Type>());
+    }
+
+    [Fact]
+    public async Task Cannot_delete_concrete_base_resource_at_concrete_derived_endpoint()
+    {
+        // Arrange
+        Bike existingBike = _fakers.Bike.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingBike);
+            await dbContext.SaveChangesAsync();
+        });
+
+        string route = $"/tandems/{existingBike.StringId}";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteDeleteAsync<Document>(route);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested resource does not exist.");
+        error.Detail.Should().Be($"Resource of type 'tandems' with ID '{existingBike.StringId}' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_set_abstract_resource_at_abstract_ToOne_relationship_endpoint()
+    {
+        // Arrange
+        var carbonWheelStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<CarbonWheel, long>>();
+
+        CarbonWheel existingCarbonWheel = _fakers.CarbonWheel.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Wheels.Add(existingCarbonWheel);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "vehicles",
+                id = existingTandem.StringId
+            }
+        };
+
+        string route = $"/wheels/{existingCarbonWheel.StringId}/relationships/vehicle";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Wheel wheelInDatabase = await dbContext.Wheels.Include(wheel => wheel.Vehicle).FirstWithIdAsync(existingCarbonWheel.Id);
+
+            wheelInDatabase.Should().BeOfType<CarbonWheel>();
+
+            wheelInDatabase.Vehicle.ShouldNotBeNull();
+            wheelInDatabase.Vehicle.Should().BeOfType<Tandem>();
+            wheelInDatabase.Vehicle.Id.Should().Be(existingTandem.Id);
+        });
+
+        carbonWheelStore.AssertLeftType<CarbonWheel>();
+        carbonWheelStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Can_set_abstract_resources_at_abstract_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            dbContext.Wheels.Add(existingChromeWheel);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "wheels",
+                    id = existingChromeWheel.StringId
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingTandem.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Vehicle vehicleInDatabase = await dbContext.Vehicles.Include(vehicle => vehicle.Wheels).FirstWithIdAsync(existingTandem.Id);
+
+            vehicleInDatabase.Should().BeOfType<Tandem>();
+
+            vehicleInDatabase.Wheels.ShouldHaveCount(1);
+            vehicleInDatabase.Wheels.ElementAt(0).Should().BeOfType<ChromeWheel>();
+            vehicleInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingChromeWheel.Id);
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(typeof(ChromeWheel));
+    }
+
+    [Fact]
+    public async Task Can_set_concrete_base_resource_stored_as_derived_at_abstract_ToOne_relationship_endpoint()
+    {
+        // Arrange
+        var carbonWheelStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<CarbonWheel, long>>();
+
+        CarbonWheel existingCarbonWheel = _fakers.CarbonWheel.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Wheels.Add(existingCarbonWheel);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "bikes",
+                id = existingTandem.StringId
+            }
+        };
+
+        string route = $"/wheels/{existingCarbonWheel.StringId}/relationships/vehicle";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Wheel wheelInDatabase = await dbContext.Wheels.Include(wheel => wheel.Vehicle).FirstWithIdAsync(existingCarbonWheel.Id);
+
+            wheelInDatabase.Should().BeOfType<CarbonWheel>();
+
+            wheelInDatabase.Vehicle.ShouldNotBeNull();
+            wheelInDatabase.Vehicle.Should().BeOfType<Tandem>();
+            wheelInDatabase.Vehicle.Id.Should().Be(existingTandem.Id);
+        });
+
+        carbonWheelStore.AssertLeftType<CarbonWheel>();
+        carbonWheelStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Can_set_concrete_base_resources_stored_as_derived_at_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var manufacturerStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<VehicleManufacturer, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "bikes",
+                    id = existingTandem.StringId
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}/relationships/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePatchAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            VehicleManufacturer manufacturerInDatabase = await dbContext.VehicleManufacturers.Include(manufacturer => manufacturer.Vehicles)
+                .FirstWithIdAsync(existingManufacturer.Id);
+
+            manufacturerInDatabase.Vehicles.ShouldHaveCount(1);
+            manufacturerInDatabase.Vehicles.ElementAt(0).Should().BeOfType<Tandem>();
+            manufacturerInDatabase.Vehicles.ElementAt(0).Id.Should().Be(existingTandem.Id);
+        });
+
+        manufacturerStore.AssertLeftType<VehicleManufacturer>();
+        manufacturerStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Cannot_set_concrete_derived_resource_stored_as_concrete_base_at_abstract_ToOne_relationship_endpoint()
+    {
+        // Arrange
+        CarbonWheel existingCarbonWheel = _fakers.CarbonWheel.Generate();
+
+        Bike existingBike = _fakers.Bike.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Wheels.Add(existingCarbonWheel);
+            dbContext.Vehicles.Add(existingBike);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new
+            {
+                type = "tandems",
+                id = existingBike.StringId
+            }
+        };
+
+        string route = $"/wheels/{existingCarbonWheel.StringId}/relationships/vehicle";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'tandems' with ID '{existingBike.StringId}' in relationship 'vehicle' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_set_concrete_derived_resources_stored_as_sibling_derived_at_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        Truck existingTruck = _fakers.Truck.Generate();
+        existingTruck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            dbContext.Vehicles.Add(existingTruck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "cars",
+                    id = existingTruck.StringId
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}/relationships/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'cars' with ID '{existingTruck.StringId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_set_unknown_resources_at_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        string unknownTruckId = Unknown.StringId.For<Truck, long>();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "trucks",
+                    id = unknownTruckId
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}/relationships/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{unknownTruckId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_clear_ToOne_relationship_for_left_type_stored_as_sibling_type()
+    {
+        Truck existingTruck = _fakers.Truck.Generate();
+        existingTruck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTruck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = (object?)null
+        };
+
+        string route = $"/cars/{existingTruck.StringId}/relationships/engine";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePatchAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested resource does not exist.");
+        error.Detail.Should().Be($"Resource of type 'cars' with ID '{existingTruck.StringId}' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_add_abstract_resources_at_abstract_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+        existingTandem.Wheels = _fakers.CarbonWheel.Generate(1).Cast<Wheel>().ToHashSet();
+
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            dbContext.Wheels.Add(existingChromeWheel);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "wheels",
+                    id = existingChromeWheel.StringId
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingTandem.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePostAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Vehicle vehicleInDatabase = await dbContext.Vehicles.Include(vehicle => vehicle.Wheels).FirstWithIdAsync(existingTandem.Id);
+
+            vehicleInDatabase.Should().BeOfType<Tandem>();
+
+            vehicleInDatabase.Wheels.ShouldHaveCount(2);
+            vehicleInDatabase.Wheels.ElementAt(0).Should().BeOfType<CarbonWheel>();
+            vehicleInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingTandem.Wheels.ElementAt(0).Id);
+            vehicleInDatabase.Wheels.ElementAt(1).Should().BeOfType<ChromeWheel>();
+            vehicleInDatabase.Wheels.ElementAt(1).Id.Should().Be(existingChromeWheel.Id);
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(typeof(ChromeWheel));
+    }
+
+    [Fact]
+    public async Task Can_add_concrete_derived_resources_at_abstract_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+        existingTandem.Wheels = _fakers.CarbonWheel.Generate(1).Cast<Wheel>().ToHashSet();
+
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            dbContext.Wheels.Add(existingChromeWheel);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "chromeWheels",
+                    id = existingChromeWheel.StringId
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingTandem.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePostAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Vehicle vehicleInDatabase = await dbContext.Vehicles.Include(vehicle => vehicle.Wheels).FirstWithIdAsync(existingTandem.Id);
+
+            vehicleInDatabase.Should().BeOfType<Tandem>();
+
+            vehicleInDatabase.Wheels.ShouldHaveCount(2);
+            vehicleInDatabase.Wheels.ElementAt(0).Should().BeOfType<CarbonWheel>();
+            vehicleInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingTandem.Wheels.ElementAt(0).Id);
+            vehicleInDatabase.Wheels.ElementAt(1).Should().BeOfType<ChromeWheel>();
+            vehicleInDatabase.Wheels.ElementAt(1).Id.Should().Be(existingChromeWheel.Id);
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(typeof(ChromeWheel));
+    }
+
+    [Fact]
+    public async Task Can_add_concrete_base_resources_stored_as_derived_at_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var manufacturerStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<VehicleManufacturer, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+        existingManufacturer.Vehicles = _fakers.Car.Generate(1).Cast<Vehicle>().ToHashSet();
+        ((Car)existingManufacturer.Vehicles.ElementAt(0)).Engine = _fakers.GasolineEngine.Generate();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Set<VehicleManufacturer>().Add(existingManufacturer);
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "bikes",
+                    id = existingTandem.StringId
+                }
+            }
+        };
+
+        string route = $"vehicleManufacturers/{existingManufacturer.StringId}/relationships/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecutePostAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            VehicleManufacturer manufacturerInDatabase = await dbContext.Set<VehicleManufacturer>().Include(manufacturer => manufacturer.Vehicles)
+                .FirstWithIdAsync(existingManufacturer.Id);
+
+            manufacturerInDatabase.Vehicles.ShouldHaveCount(2);
+            manufacturerInDatabase.Vehicles.ElementAt(0).Should().BeOfType<Car>();
+            manufacturerInDatabase.Vehicles.ElementAt(0).Id.Should().Be(existingManufacturer.Vehicles.ElementAt(0).Id);
+            manufacturerInDatabase.Vehicles.ElementAt(1).Should().BeOfType<Tandem>();
+            manufacturerInDatabase.Vehicles.ElementAt(1).Id.Should().Be(existingTandem.Id);
+        });
+
+        manufacturerStore.AssertLeftType<VehicleManufacturer>();
+        manufacturerStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Cannot_add_concrete_derived_resources_stored_as_sibling_derived_at_abstract_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        Bike existingBike = _fakers.Bike.Generate();
+
+        ChromeWheel existingChromeWheel = _fakers.ChromeWheel.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingBike);
+            dbContext.Wheels.Add(existingChromeWheel);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "carbonWheels",
+                    id = existingChromeWheel.StringId
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingBike.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'carbonWheels' with ID '{existingChromeWheel.StringId}' in relationship 'wheels' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_add_unknown_resources_at_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        string unknownTruckId = Unknown.StringId.For<Truck, long>();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "trucks",
+                    id = unknownTruckId
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}/relationships/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{unknownTruckId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_add_to_ToMany_relationship_for_left_type_stored_as_sibling_type()
+    {
+        Truck existingTruck = _fakers.Truck.Generate();
+        existingTruck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTruck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = Array.Empty<object>()
+        };
+
+        string route = $"/cars/{existingTruck.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecutePostAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested resource does not exist.");
+        error.Detail.Should().Be($"Resource of type 'cars' with ID '{existingTruck.StringId}' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Can_remove_abstract_resources_at_abstract_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+        existingTandem.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "wheels",
+                    id = existingTandem.Wheels.ElementAt(0).StringId
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingTandem.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecuteDeleteAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Vehicle vehicleInDatabase = await dbContext.Vehicles.Include(vehicle => vehicle.Wheels).FirstWithIdAsync(existingTandem.Id);
+
+            vehicleInDatabase.Should().BeOfType<Tandem>();
+
+            vehicleInDatabase.Wheels.ShouldHaveCount(1);
+            vehicleInDatabase.Wheels.ElementAt(0).Should().BeOfType<ChromeWheel>();
+            vehicleInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingTandem.Wheels.ElementAt(1).Id);
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(typeof(ChromeWheel));
+    }
+
+    [Fact]
+    public async Task Can_remove_concrete_derived_resources_at_abstract_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var tandemStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<Tandem, long>>();
+
+        Tandem existingTandem = _fakers.Tandem.Generate();
+        existingTandem.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTandem);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "chromeWheels",
+                    id = existingTandem.Wheels.ElementAt(0).StringId
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingTandem.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecuteDeleteAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            Vehicle vehicleInDatabase = await dbContext.Vehicles.Include(vehicle => vehicle.Wheels).FirstWithIdAsync(existingTandem.Id);
+
+            vehicleInDatabase.Should().BeOfType<Tandem>();
+
+            vehicleInDatabase.Wheels.ShouldHaveCount(1);
+            vehicleInDatabase.Wheels.ElementAt(0).Should().BeOfType<ChromeWheel>();
+            vehicleInDatabase.Wheels.ElementAt(0).Id.Should().Be(existingTandem.Wheels.ElementAt(1).Id);
+        });
+
+        tandemStore.AssertLeftType<Tandem>();
+        tandemStore.AssertRightTypes(typeof(ChromeWheel));
+    }
+
+    [Fact]
+    public async Task Can_remove_concrete_base_resources_stored_as_derived_at_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        var manufacturerStore = _testContext.Factory.Services.GetRequiredService<ResourceTypeCaptureStore<VehicleManufacturer, long>>();
+
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+        existingManufacturer.Vehicles = _fakers.Tandem.Generate(1).Cast<Vehicle>().Concat(_fakers.Car.Generate(1)).ToHashSet();
+        ((Car)existingManufacturer.Vehicles.ElementAt(1)).Engine = _fakers.GasolineEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Set<VehicleManufacturer>().Add(existingManufacturer);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "bikes",
+                    id = existingManufacturer.Vehicles.ElementAt(0).StringId
+                }
+            }
+        };
+
+        string route = $"vehicleManufacturers/{existingManufacturer.StringId}/relationships/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, string responseDocument) = await _testContext.ExecuteDeleteAsync<string>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NoContent);
+
+        responseDocument.Should().BeEmpty();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            VehicleManufacturer manufacturerInDatabase = await dbContext.Set<VehicleManufacturer>().Include(manufacturer => manufacturer.Vehicles)
+                .FirstWithIdAsync(existingManufacturer.Id);
+
+            manufacturerInDatabase.Vehicles.ShouldHaveCount(1);
+            manufacturerInDatabase.Vehicles.ElementAt(0).Should().BeOfType<Car>();
+            manufacturerInDatabase.Vehicles.ElementAt(0).Id.Should().Be(existingManufacturer.Vehicles.ElementAt(1).Id);
+        });
+
+        manufacturerStore.AssertLeftType<VehicleManufacturer>();
+        manufacturerStore.AssertRightTypes(typeof(Tandem));
+    }
+
+    [Fact]
+    public async Task Cannot_remove_concrete_derived_resources_stored_as_sibling_derived_at_abstract_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        Bike existingBike = _fakers.Bike.Generate();
+        existingBike.Wheels = _fakers.ChromeWheel.Generate(2).Cast<Wheel>().ToHashSet();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingBike);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "carbonWheels",
+                    id = existingBike.Wheels.ElementAt(0).StringId
+                }
+            }
+        };
+
+        string route = $"/vehicles/{existingBike.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteDeleteAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        string? chromeWheelId = existingBike.Wheels.ElementAt(0).StringId;
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'carbonWheels' with ID '{chromeWheelId}' in relationship 'wheels' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_remove_unknown_resources_at_ToMany_relationship_endpoint()
+    {
+        // Arrange
+        VehicleManufacturer existingManufacturer = _fakers.VehicleManufacturer.Generate();
+
+        string unknownTruckId = Unknown.StringId.For<Truck, long>();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.VehicleManufacturers.Add(existingManufacturer);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = new[]
+            {
+                new
+                {
+                    type = "trucks",
+                    id = unknownTruckId
+                }
+            }
+        };
+
+        string route = $"/vehicleManufacturers/{existingManufacturer.StringId}/relationships/vehicles";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteDeleteAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("A related resource does not exist.");
+        error.Detail.Should().Be($"Related resource of type 'trucks' with ID '{unknownTruckId}' in relationship 'vehicles' does not exist.");
+        error.Source.Should().BeNull();
+    }
+
+    [Fact]
+    public async Task Cannot_remove_from_ToMany_relationship_for_left_type_stored_as_sibling_type()
+    {
+        Truck existingTruck = _fakers.Truck.Generate();
+        existingTruck.Engine = _fakers.DieselEngine.Generate();
+
+        await _testContext.RunOnDatabaseAsync(async dbContext =>
+        {
+            dbContext.Vehicles.Add(existingTruck);
+            await dbContext.SaveChangesAsync();
+        });
+
+        var requestBody = new
+        {
+            data = Array.Empty<object>()
+        };
+
+        string route = $"/cars/{existingTruck.StringId}/relationships/wheels";
+
+        // Act
+        (HttpResponseMessage httpResponse, Document responseDocument) = await _testContext.ExecuteDeleteAsync<Document>(route, requestBody);
+
+        // Assert
+        httpResponse.Should().HaveStatusCode(HttpStatusCode.NotFound);
+
+        responseDocument.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = responseDocument.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.NotFound);
+        error.Title.Should().Be("The requested resource does not exist.");
+        error.Detail.Should().Be($"Resource of type 'cars' with ID '{existingTruck.StringId}' does not exist.");
+        error.Source.Should().BeNull();
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCaptureStore.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCaptureStore.cs
new file mode 100644
index 0000000000..d9ac30f8c0
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCaptureStore.cs
@@ -0,0 +1,44 @@
+// ReSharper disable UnusedTypeParameter
+
+using FluentAssertions;
+using JsonApiDotNetCore.Middleware;
+using TestBuildingBlocks;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
+
+public sealed class ResourceTypeCaptureStore<TResource, TId>
+{
+    internal Type? LeftDeclaredType { get; set; }
+    internal string? LeftReflectedTypeName { get; set; }
+    internal ISet<string> RightTypeNames { get; } = new HashSet<string>();
+    internal IJsonApiRequest? Request { get; set; }
+
+    internal void Reset()
+    {
+        LeftDeclaredType = null;
+        LeftReflectedTypeName = null;
+        RightTypeNames.Clear();
+        Request = null;
+    }
+
+    internal void AssertLeftType<TLeft>()
+    {
+        LeftDeclaredType.Should().Be(typeof(TLeft));
+        LeftReflectedTypeName.Should().Be(typeof(TLeft).Name);
+
+        Request.ShouldNotBeNull();
+        Request.PrimaryResourceType.ShouldNotBeNull();
+        Request.PrimaryResourceType.ClrType.Should().Be(typeof(TLeft));
+        Request.Relationship?.LeftType.ClrType.Should().Be(typeof(TLeft));
+    }
+
+    internal void AssertRightTypes(params Type[] types)
+    {
+        RightTypeNames.ShouldHaveCount(types.Length);
+
+        foreach (Type type in types)
+        {
+            RightTypeNames.Should().ContainSingle(name => name == type.Name);
+        }
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCapturingDefinition.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCapturingDefinition.cs
new file mode 100644
index 0000000000..da32a75e22
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/ResourceTypeCapturingDefinition.cs
@@ -0,0 +1,120 @@
+using JetBrains.Annotations;
+using JsonApiDotNetCore;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Middleware;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Resources.Annotations;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance;
+
+/// <summary>
+/// Enables tests to verify which resource types are being observed.
+/// </summary>
+[UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
+public sealed class ResourceTypeCapturingDefinition<TResource, TId> : JsonApiResourceDefinition<TResource, TId>
+    where TResource : class, IIdentifiable<TId>
+{
+    private readonly IJsonApiRequest _request;
+    private readonly ResourceTypeCaptureStore<TResource, TId> _captureStore;
+
+    public ResourceTypeCapturingDefinition(IResourceGraph resourceGraph, IJsonApiRequest request, ResourceTypeCaptureStore<TResource, TId> captureStore)
+        : base(resourceGraph)
+    {
+        ArgumentGuard.NotNull(request, nameof(request));
+        ArgumentGuard.NotNull(captureStore, nameof(captureStore));
+
+        _request = request;
+        _captureStore = captureStore;
+    }
+
+    public override Task OnPrepareWriteAsync(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        EnsureSnapshot(resource);
+
+        return Task.CompletedTask;
+    }
+
+    public override Task<IIdentifiable?> OnSetToOneRelationshipAsync(TResource leftResource, HasOneAttribute hasOneRelationship, IIdentifiable? rightResourceId,
+        WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        EnsureSnapshot(leftResource, rightResourceId);
+
+        return Task.FromResult(rightResourceId);
+    }
+
+    public override Task OnSetToManyRelationshipAsync(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        EnsureSnapshot(leftResource, rightResourceIds);
+
+        return Task.CompletedTask;
+    }
+
+    public override Task OnAddToRelationshipAsync(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        CancellationToken cancellationToken)
+    {
+        EnsureSnapshot(leftResource, rightResourceIds);
+
+        return Task.CompletedTask;
+    }
+
+    public override Task OnRemoveFromRelationshipAsync(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        CancellationToken cancellationToken)
+    {
+        EnsureSnapshot(leftResource, rightResourceIds);
+
+        return Task.CompletedTask;
+    }
+
+    public override Task OnWritingAsync(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        EnsureSnapshot(resource);
+
+        return Task.CompletedTask;
+    }
+
+    public override Task OnWriteSucceededAsync(TResource resource, WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        EnsureSnapshot(resource);
+
+        return Task.CompletedTask;
+    }
+
+    private void EnsureSnapshot(TResource leftType, IIdentifiable? rightResourceId = null)
+    {
+        IIdentifiable[] rightResourceIds = rightResourceId != null ? ArrayFactory.Create(rightResourceId) : Array.Empty<IIdentifiable>();
+
+        EnsureSnapshot(leftType, rightResourceIds);
+    }
+
+    private void EnsureSnapshot(TResource leftType, IEnumerable<IIdentifiable> rightResourceIds)
+    {
+        if (_captureStore.Request == null)
+        {
+            _captureStore.Request = TakeRequestSnapshot();
+            _captureStore.LeftDeclaredType = typeof(TResource);
+            _captureStore.LeftReflectedTypeName = leftType.GetType().Name;
+        }
+        else
+        {
+            if (leftType.GetType().Name != _captureStore.LeftReflectedTypeName)
+            {
+                throw new InvalidOperationException(
+                    $"Reflected left type changed from '{_captureStore.LeftReflectedTypeName}' to '{leftType.GetType().Name}'.");
+            }
+        }
+
+        foreach (IIdentifiable rightResourceId in rightResourceIds)
+        {
+            _captureStore.RightTypeNames.Add(rightResourceId.GetType().Name);
+        }
+    }
+
+    private IJsonApiRequest TakeRequestSnapshot()
+    {
+        var requestSnapshot = new JsonApiRequest();
+        requestSnapshot.CopyFrom(_request);
+
+        return requestSnapshot;
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyWriteTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyWriteTests.cs
new file mode 100644
index 0000000000..edd81659e8
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerHierarchy/TablePerHierarchyWriteTests.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using TestBuildingBlocks;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerHierarchy;
+
+[UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
+public sealed class TablePerHierarchyWriteTests : ResourceInheritanceWriteTests<TablePerHierarchyDbContext>
+{
+    public TablePerHierarchyWriteTests(IntegrationTestContext<TestableStartup<TablePerHierarchyDbContext>, TablePerHierarchyDbContext> testContext)
+        : base(testContext)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeWriteTests.cs b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeWriteTests.cs
new file mode 100644
index 0000000000..ed98334583
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/IntegrationTests/ResourceInheritance/TablePerType/TablePerTypeWriteTests.cs
@@ -0,0 +1,13 @@
+using JetBrains.Annotations;
+using TestBuildingBlocks;
+
+namespace JsonApiDotNetCoreTests.IntegrationTests.ResourceInheritance.TablePerType;
+
+[UsedImplicitly(ImplicitUseKindFlags.InstantiatedNoFixedConstructorSignature)]
+public sealed class TablePerTypeWriteTests : ResourceInheritanceWriteTests<TablePerTypeDbContext>
+{
+    public TablePerTypeWriteTests(IntegrationTestContext<TestableStartup<TablePerTypeDbContext>, TablePerTypeDbContext> testContext)
+        : base(testContext)
+    {
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs
index 17218acb39..8cd108deae 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Response/FakeResourceDefinitionAccessor.cs
@@ -64,9 +64,9 @@ public Task OnSetToManyRelationshipAsync<TResource>(TResource leftResource, HasM
         return Task.CompletedTask;
     }
 
-    public Task OnAddToRelationshipAsync<TResource, TId>(TId leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+    public Task OnAddToRelationshipAsync<TResource>(TResource leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
         CancellationToken cancellationToken)
-        where TResource : class, IIdentifiable<TId>
+        where TResource : class, IIdentifiable
     {
         return Task.CompletedTask;
     }
diff --git a/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs b/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs
index 3213adcbe6..344668c800 100644
--- a/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs
+++ b/test/UnitTests/Extensions/ServiceCollectionExtensionsTests.cs
@@ -315,7 +315,7 @@ public Task<int> CountAsync(FilterExpression? filter, CancellationToken cancella
             throw new NotImplementedException();
         }
 
-        public Task<ResourceOfInt32> GetForCreateAsync(int id, CancellationToken cancellationToken)
+        public Task<ResourceOfInt32> GetForCreateAsync(Type resourceClrType, int id, CancellationToken cancellationToken)
         {
             throw new NotImplementedException();
         }
@@ -335,7 +335,7 @@ public Task UpdateAsync(ResourceOfInt32 resourceFromRequest, ResourceOfInt32 res
             throw new NotImplementedException();
         }
 
-        public Task DeleteAsync(int id, CancellationToken cancellationToken)
+        public Task DeleteAsync(ResourceOfInt32? resourceFromDatabase, int id, CancellationToken cancellationToken)
         {
             throw new NotImplementedException();
         }
@@ -345,7 +345,8 @@ public Task SetRelationshipAsync(ResourceOfInt32 leftResource, object? rightValu
             throw new NotImplementedException();
         }
 
-        public Task AddToToManyRelationshipAsync(int leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
+        public Task AddToToManyRelationshipAsync(ResourceOfInt32? leftResource, int leftId, ISet<IIdentifiable> rightResourceIds,
+            CancellationToken cancellationToken)
         {
             throw new NotImplementedException();
         }
@@ -369,7 +370,7 @@ public Task<int> CountAsync(FilterExpression? filter, CancellationToken cancella
             throw new NotImplementedException();
         }
 
-        public Task<ResourceOfGuid> GetForCreateAsync(Guid id, CancellationToken cancellationToken)
+        public Task<ResourceOfGuid> GetForCreateAsync(Type resourceClrType, Guid id, CancellationToken cancellationToken)
         {
             throw new NotImplementedException();
         }
@@ -389,7 +390,7 @@ public Task UpdateAsync(ResourceOfGuid resourceFromRequest, ResourceOfGuid resou
             throw new NotImplementedException();
         }
 
-        public Task DeleteAsync(Guid id, CancellationToken cancellationToken)
+        public Task DeleteAsync(ResourceOfGuid? resourceFromDatabase, Guid id, CancellationToken cancellationToken)
         {
             throw new NotImplementedException();
         }
@@ -399,7 +400,8 @@ public Task SetRelationshipAsync(ResourceOfGuid leftResource, object? rightValue
             throw new NotImplementedException();
         }
 
-        public Task AddToToManyRelationshipAsync(Guid leftId, ISet<IIdentifiable> rightResourceIds, CancellationToken cancellationToken)
+        public Task AddToToManyRelationshipAsync(ResourceOfGuid? leftResource, Guid leftId, ISet<IIdentifiable> rightResourceIds,
+            CancellationToken cancellationToken)
         {
             throw new NotImplementedException();
         }
@@ -465,7 +467,7 @@ public Task OnSetToManyRelationshipAsync(ResourceOfInt32 leftResource, HasManyAt
             throw new NotImplementedException();
         }
 
-        public Task OnAddToRelationshipAsync(int leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        public Task OnAddToRelationshipAsync(ResourceOfInt32 leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
             CancellationToken cancellationToken)
         {
             throw new NotImplementedException();
@@ -553,7 +555,7 @@ public Task OnSetToManyRelationshipAsync(ResourceOfGuid leftResource, HasManyAtt
             throw new NotImplementedException();
         }
 
-        public Task OnAddToRelationshipAsync(Guid leftResourceId, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
+        public Task OnAddToRelationshipAsync(ResourceOfGuid leftResource, HasManyAttribute hasManyRelationship, ISet<IIdentifiable> rightResourceIds,
             CancellationToken cancellationToken)
         {
             throw new NotImplementedException();

From 0333a01b3503fcd43fc94c403b034f4b9b648dfc Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Thu, 31 Mar 2022 17:25:25 +0200
Subject: [PATCH 15/19] Updated documentation

---
 docs/usage/reading/filtering.md     |  26 ++
 docs/usage/resources/inheritance.md | 408 ++++++++++++++++++++++++++++
 docs/usage/toc.md                   |   1 +
 3 files changed, 435 insertions(+)
 create mode 100644 docs/usage/resources/inheritance.md

diff --git a/docs/usage/reading/filtering.md b/docs/usage/reading/filtering.md
index dab1fdb6e2..285f3b5a98 100644
--- a/docs/usage/reading/filtering.md
+++ b/docs/usage/reading/filtering.md
@@ -24,6 +24,7 @@ Expressions are composed using the following functions:
 | Ends with text                | `endsWith`         | `?filter=endsWith(description,'End')`                 |
 | Equals one value from set     | `any`              | `?filter=any(chapter,'Intro','Summary','Conclusion')` |
 | Collection contains items     | `has`              | `?filter=has(articles)`                               |
+| Type-check derived type (v5)  | `isType`           | `?filter=isType(,men)`                                |
 | Negation                      | `not`              | `?filter=not(equals(lastName,null))`                  |
 | Conditional logical OR        | `or`               | `?filter=or(has(orders),has(invoices))`               |
 | Conditional logical AND       | `and`              | `?filter=and(has(orders),has(invoices))`              |
@@ -86,6 +87,31 @@ GET /customers?filter=has(orders,not(equals(status,'Paid'))) HTTP/1.1
 
 Which returns only customers that have at least one unpaid order.
 
+_since v5.0_
+
+Use the `isType` filter function to perform a type check on a derived type. You can pass a nested filter, where the derived fields are accessible.
+The first parameter can be used to perform the type check on a to-one relationship path.
+
+Only return men:
+```http
+GET /humans?filter=isType(,men) HTTP/1.1
+```
+
+Only return men with beards:
+```http
+GET /humans?filter=isType(,men,equals(hasBeard,'true')) HTTP/1.1
+```
+
+Only return people whose best friend is a man with children:
+```http
+GET /humans?filter=isType(bestFriend,men,has(children)) HTTP/1.1
+```
+
+Only return people who have at least one female married child:
+```http
+GET /humans?filter=has(children,isType(,woman,not(equals(husband,null)))) HTTP/1.1
+```
+
 # Legacy filters
 
 The next section describes how filtering worked in versions prior to v4.0. They are always applied on the set of resources being requested (no nesting).
diff --git a/docs/usage/resources/inheritance.md b/docs/usage/resources/inheritance.md
new file mode 100644
index 0000000000..864a38bea1
--- /dev/null
+++ b/docs/usage/resources/inheritance.md
@@ -0,0 +1,408 @@
+# Resource inheritance
+
+_since v5.0_
+
+Resource classes can be part of a type hierarchy. For example:
+
+```c#
+#nullable enable
+
+public abstract class Human : Identifiable<long>
+{
+    [Attr]
+    public string Name { get; set; } = null!;
+
+    [HasOne]
+    public Man? Father { get; set; }
+
+    [HasOne]
+    public Woman? Mother { get; set; }
+
+    [HasMany]
+    public ISet<Human> Children { get; set; } = new HashSet<Human>();
+
+    [HasOne]
+    public Human? BestFriend { get; set; }
+}
+
+public sealed class Man : Human
+{
+    [Attr]
+    public bool HasBeard { get; set; }
+
+    [HasOne]
+    public Woman? Wife { get; set; }
+}
+
+public sealed class Woman : Human
+{
+    [Attr]
+    public string? MaidenName { get; set; }
+
+    [HasOne]
+    public Man? Husband { get; set; }
+}
+```
+
+## Reading data
+
+You can access them through base or derived endpoints.
+
+```http
+GET /humans HTTP/1.1
+
+{
+  "data": [
+    {
+      "type": "women",
+      "id": "1",
+      "attributes": {
+        "maidenName": "Smith",
+        "name": "Jane Doe"
+      },
+      "relationships": {
+        "husband": {
+          "links": {
+            "self": "/women/1/relationships/husband",
+            "related": "/women/1/husband"
+          }
+        },
+        "father": {
+          "links": {
+            "self": "/women/1/relationships/father",
+            "related": "/women/1/father"
+          }
+        },
+        "mother": {
+          "links": {
+            "self": "/women/1/relationships/mother",
+            "related": "/women/1/mother"
+          }
+        },
+        "children": {
+          "links": {
+            "self": "/women/1/relationships/children",
+            "related": "/women/1/children"
+          }
+        },
+        "bestFriend": {
+          "links": {
+            "self": "/women/1/relationships/bestFriend",
+            "related": "/women/1/bestFriend"
+          }
+        }
+      },
+      "links": {
+        "self": "/women/1"
+      }
+    },
+    {
+      "type": "men",
+      "id": "2",
+      "attributes": {
+        "hasBeard": true,
+        "name": "John Doe"
+      },
+      "relationships": {
+        "wife": {
+          "links": {
+            "self": "/men/2/relationships/wife",
+            "related": "/men/2/wife"
+          }
+        },
+        "father": {
+          "links": {
+            "self": "/men/2/relationships/father",
+            "related": "/men/2/father"
+          }
+        },
+        "mother": {
+          "links": {
+            "self": "/men/2/relationships/mother",
+            "related": "/men/2/mother"
+          }
+        },
+        "children": {
+          "links": {
+            "self": "/men/2/relationships/children",
+            "related": "/men/2/children"
+          }
+        },
+        "bestFriend": {
+          "links": {
+            "self": "/men/2/relationships/bestFriend",
+            "related": "/men/2/bestFriend"
+          }
+        }
+      },
+      "links": {
+        "self": "/men/2"
+      }
+    }
+  ]
+}
+```
+
+### Spare fieldsets
+
+If you only want to retrieve the fields from the base type, you can use [sparse fieldsets](~/usage/reading/sparse-fieldset-selection.md).
+
+```http
+GET /humans?fields[men]=name,children&fields[women]=name,children HTTP/1.1
+```
+
+### Includes
+
+Relationships on derived types can be included without special syntax.
+
+```http
+GET /humans?include=husband,wife,children HTTP/1.1
+```
+
+### Sorting
+
+Just like includes, you can sort on derived attributes and relationships.
+
+```http
+GET /humans?sort=maidenName,wife.name HTTP/1.1
+```
+
+This returns all women sorted by their maiden names, followed by all men sorted by the name of their wife.
+
+To accomplish the same from a [Resource Definition](~/usage/extensibility/resource-definitions.md), upcast to the derived type:
+
+```c#
+public override SortExpression OnApplySort(SortExpression? existingSort)
+{
+    return CreateSortExpressionFromLambda(new PropertySortOrder
+    {
+        (human => ((Woman)human).MaidenName, ListSortDirection.Ascending),
+        (human => ((Man)human).Wife!.Name, ListSortDirection.Ascending)
+    });
+}
+```
+
+### Filtering
+
+Use the `isType` filter function to perform a type check on a derived type. You can pass a nested filter, where the derived fields are accessible.
+The first parameter can be used to perform the type check on a to-one relationship path.
+
+Only return men:
+```http
+GET /humans?filter=isType(,men) HTTP/1.1
+```
+
+Only return men with beards:
+```http
+GET /humans?filter=isType(,men,equals(hasBeard,'true')) HTTP/1.1
+```
+
+Only return people whose best friend is a man with children:
+```http
+GET /humans?filter=isType(bestFriend,men,has(children)) HTTP/1.1
+```
+
+Only return people who have at least one female married child:
+```http
+GET /humans?filter=has(children,isType(,woman,not(equals(husband,null)))) HTTP/1.1
+```
+
+## Writing data
+
+Just like reading data, you can use base or derived endpoints. When using relationships in request bodies, you can use base or derived types as well.
+The only exception is that you cannot use an abstract base type in the request body when creating or updating a resource.
+
+For example, updating an attribute and relationship can be done at an abstract endpoint, but its body requires non-abstract types:
+
+```http
+PATCH /humans/2 HTTP/1.1
+
+{
+  "data": {
+    "type": "men",
+    "id": "2",
+    "attributes": {
+      "hasBeard": false
+    },
+    "relationships": {
+      "wife": {
+        "data": {
+          "type": "women",
+          "id": "1"
+        }
+      }
+    }
+  }
+}
+```
+
+Updating a relationship does allow abstract types. For example:
+
+```http
+PATCH /humans/1/relationships/children HTTP/1.1
+
+{
+  "data": [
+    {
+      "type": "humans",
+      "id": "2"
+    }
+  ]
+}
+```
+
+### Request pipeline
+
+The `TResource` type parameter used in controllers, resource services and resource repositories always matches the used endpoint.
+But when JsonApiDotNetCore sees usage of a type from a type hierarchy, it fetches the stored types and updates `IJsonApiRequest` accordingly.
+As a result, `TResource` can be different from what `IJsonApiRequest.PrimaryResourceType` returns.
+
+For example, on the request:
+```http
+ GET /humans/1 HTTP/1.1
+```
+
+JsonApiDotNetCore runs `IResourceService<Human, long>`, but `IJsonApiRequest.PrimaryResourceType` returns `Woman`
+if human with ID 1 is stored as a woman in the underlying data store.
+
+Even with a simple type hierarchy as used here, lots of possible combinations quickly arise. For example, changing someone's best friend can be done using the following requests:
+- `PATCH /humans/1/ { "data": { relationships: { bestFriend: { type: "women" ... } } } }`
+- `PATCH /humans/1/ { "data": { relationships: { bestFriend: { type: "men" ... } } } }`
+- `PATCH /women/1/ { "data": { relationships: { bestFriend: { type: "women" ... } } } }`
+- `PATCH /women/1/ { "data": { relationships: { bestFriend: { type: "men" ... } } } }`
+- `PATCH /men/2/ { "data": { relationships: { bestFriend: { type: "women" ... } } } }`
+- `PATCH /men/2/ { "data": { relationships: { bestFriend: { type: "men" ... } } } }`
+- `PATCH /humans/1/relationships/bestFriend { "data": { type: "human" ... } }`
+- `PATCH /humans/1/relationships/bestFriend { "data": { type: "women" ... } }`
+- `PATCH /humans/1/relationships/bestFriend { "data": { type: "men" ... } }`
+- `PATCH /women/1/relationships/bestFriend { "data": { type: "human" ... } }`
+- `PATCH /women/1/relationships/bestFriend { "data": { type: "women" ... } }`
+- `PATCH /women/1/relationships/bestFriend { "data": { type: "men" ... } }`
+- `PATCH /men/2/relationships/bestFriend { "data": { type: "human" ... } }`
+- `PATCH /men/2/relationships/bestFriend { "data": { type: "women" ... } }`
+- `PATCH /men/2/relationships/bestFriend { "data": { type: "men" ... } }`
+
+Because of all the possible combinations, implementing business rules in the pipeline is a no-go.
+Resource definitions provide a better solution, see below.
+
+### Resource definitions
+
+In contract to the request pipeline, JsonApiDotNetCore always executes the resource definition that matches the *stored* type.
+This enables to implement business logic in a central place, irrespective of which endpoint was used or whether base types were used in relationships.
+
+To delegate logic for base types to their matching resource type, you can build a chain of resource definitions. And because you'll always get the
+actually stored types (for relationships too), you can type-check left-side and right-side types in resources definitions.
+
+```c#
+public sealed class HumanDefinition : JsonApiResourceDefinition<Human, long>
+{
+    public HumanDefinition(IResourceGraph resourceGraph)
+        : base(resourceGraph)
+    {
+    }
+
+    public override Task<IIdentifiable?> OnSetToOneRelationshipAsync(Human leftResource,
+        HasOneAttribute hasOneRelationship, IIdentifiable? rightResourceId,
+        WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        if (leftResource is Man &&
+            hasOneRelationship.Property.Name == nameof(Human.BestFriend) &&
+            rightResourceId is Woman)
+        {
+            throw new Exception("Men are not supposed to have a female best friend.");
+        }
+
+        return Task.FromResult(rightResourceId);
+    }
+
+    public override Task OnWritingAsync(Human resource, WriteOperationKind writeOperation,
+        CancellationToken cancellationToken)
+    {
+        if (writeOperation is WriteOperationKind.CreateResource or
+            WriteOperationKind.UpdateResource)
+        {
+            if (resource is Man { HasBeard: true })
+            {
+                throw new Exception("Only shaved men, please.");
+            }
+        }
+
+        return Task.CompletedTask;
+    }
+}
+
+public sealed class WomanDefinition : JsonApiResourceDefinition<Woman, long>
+{
+    private readonly IResourceDefinition<Human, long> _baseDefinition;
+
+    public WomanDefinition(IResourceGraph resourceGraph,
+        IResourceDefinition<Human, long> baseDefinition)
+        : base(resourceGraph)
+    {
+        _baseDefinition = baseDefinition;
+    }
+
+    public override Task<IIdentifiable?> OnSetToOneRelationshipAsync(Woman leftResource,
+        HasOneAttribute hasOneRelationship, IIdentifiable? rightResourceId,
+        WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        if (ResourceType.BaseType!.FindRelationshipByPublicName(
+            hasOneRelationship.PublicName) != null)
+        {
+            // Delegate to resource definition for base type Human.
+            return _baseDefinition.OnSetToOneRelationshipAsync(leftResource,
+                hasOneRelationship, rightResourceId, writeOperation, cancellationToken);
+        }
+
+        // Handle here.
+        if (hasOneRelationship.Property.Name == nameof(Woman.Husband) &&
+            rightResourceId == null)
+        {
+            throw new Exception("We don't accept unmarried women at this time.");
+        }
+
+        return Task.FromResult(rightResourceId);
+    }
+
+    public override async Task OnPrepareWriteAsync(Woman resource,
+        WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        // Run rules in resource definition for base type Human.
+        await _baseDefinition.OnPrepareWriteAsync(resource, writeOperation, cancellationToken);
+
+        // Run rules for type Woman.
+        if (resource.MaidenName == null)
+        {
+            throw new Exception("Women should have a maiden name.");
+        }
+    }
+}
+
+public sealed class ManDefinition : JsonApiResourceDefinition<Man, long>
+{
+    private readonly IResourceDefinition<Human, long> _baseDefinition;
+
+    public ManDefinition(IResourceGraph resourceGraph,
+        IResourceDefinition<Human, long> baseDefinition)
+        : base(resourceGraph)
+    {
+        _baseDefinition = baseDefinition;
+    }
+
+    public override Task<IIdentifiable?> OnSetToOneRelationshipAsync(Man leftResource,
+        HasOneAttribute hasOneRelationship, IIdentifiable? rightResourceId,
+        WriteOperationKind writeOperation, CancellationToken cancellationToken)
+    {
+        // No man-specific logic, but we'll still need to delegate.
+        return _baseDefinition.OnSetToOneRelationshipAsync(leftResource, hasOneRelationship,
+            rightResourceId, writeOperation, cancellationToken);
+    }
+
+    public override Task OnWritingAsync(Man resource, WriteOperationKind writeOperation,
+        CancellationToken cancellationToken)
+    {
+        // No man-specific logic, but we'll still need to delegate.
+        return _baseDefinition.OnWritingAsync(resource, writeOperation, cancellationToken);
+    }
+}
+```
diff --git a/docs/usage/toc.md b/docs/usage/toc.md
index f6924036ea..c30a2b0f37 100644
--- a/docs/usage/toc.md
+++ b/docs/usage/toc.md
@@ -1,6 +1,7 @@
 # [Resources](resources/index.md)
 ## [Attributes](resources/attributes.md)
 ## [Relationships](resources/relationships.md)
+## [Inheritance](resources/inheritance.md)
 ## [Nullability](resources/nullability.md)
 
 # Reading data

From 6738a09d563a0b63c3a15aef006d38821d8377ad Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Thu, 31 Mar 2022 19:37:53 +0200
Subject: [PATCH 16/19] Added rewriter unit tests to improve code coverage

---
 .../Queries/QueryExpressionRewriterTests.cs   | 212 ++++++++++++++++++
 .../TestableQueryExpressionRewriter.cs        | 151 +++++++++++++
 2 files changed, 363 insertions(+)
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Queries/QueryExpressionRewriterTests.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Queries/TestableQueryExpressionRewriter.cs

diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Queries/QueryExpressionRewriterTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/Queries/QueryExpressionRewriterTests.cs
new file mode 100644
index 0000000000..d167bab60b
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Queries/QueryExpressionRewriterTests.cs
@@ -0,0 +1,212 @@
+using System.Collections.Immutable;
+using System.ComponentModel.Design;
+using FluentAssertions;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Queries.Expressions;
+using JsonApiDotNetCore.Queries.Internal.Parsing;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCoreTests.IntegrationTests.QueryStrings;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Queries;
+
+public sealed class QueryExpressionRewriterTests
+{
+    private static readonly IResourceFactory ResourceFactory = new ResourceFactory(new ServiceContainer());
+
+    // @formatter:wrap_chained_method_calls chop_always
+    // @formatter:keep_existing_linebreaks true
+
+    private static readonly IResourceGraph ResourceGraph = new ResourceGraphBuilder(new JsonApiOptions(), NullLoggerFactory.Instance)
+        .Add<Blog, int>()
+        .Add<BlogPost, int>()
+        .Add<Label, int>()
+        .Add<Comment, int>()
+        .Add<WebAccount, int>()
+        .Add<Human, int>()
+        .Add<Man, int>()
+        .Add<Woman, int>()
+        .Add<AccountPreferences, int>()
+        .Add<LoginAttempt, int>()
+        .Build();
+
+    // @formatter:wrap_chained_method_calls restore
+    // @formatter:keep_existing_linebreaks restore
+
+    [Theory]
+    [InlineData("posts", "Include,IncludeElement")]
+    [InlineData("posts.comments,owner.loginAttempts", "Include,IncludeElement,IncludeElement,IncludeElement,IncludeElement")]
+    public void VisitInclude(string expressionText, string expectedTypes)
+    {
+        // Arrange
+        var parser = new IncludeParser();
+        ResourceType blogType = ResourceGraph.GetResourceType<Blog>();
+
+        QueryExpression expression = parser.Parse(expressionText, blogType, null);
+        var rewriter = new TestableQueryExpressionRewriter();
+
+        // Act
+        rewriter.Visit(expression, null);
+
+        // Assert
+        List<string> visitedTypeNames = rewriter.ExpressionsVisited.Select(queryExpression => queryExpression.GetType().Name).ToList();
+        List<string> expectedTypeNames = expectedTypes.Split(',').Select(type => type + "Expression").ToList();
+
+        visitedTypeNames.Should().ContainInOrder(expectedTypeNames);
+        visitedTypeNames.Should().HaveCount(expectedTypeNames.Count);
+    }
+
+    [Theory]
+    [InlineData("title", "SparseFieldSet")]
+    [InlineData("title,posts", "SparseFieldSet")]
+    public void VisitSparseFieldSet(string expressionText, string expectedTypes)
+    {
+        // Arrange
+        var parser = new SparseFieldSetParser();
+        ResourceType blogType = ResourceGraph.GetResourceType<Blog>();
+
+        QueryExpression expression = parser.Parse(expressionText, blogType)!;
+        var rewriter = new TestableQueryExpressionRewriter();
+
+        // Act
+        rewriter.Visit(expression, null);
+
+        // Assert
+        List<string> visitedTypeNames = rewriter.ExpressionsVisited.Select(queryExpression => queryExpression.GetType().Name).ToList();
+        List<string> expectedTypeNames = expectedTypes.Split(',').Select(type => type + "Expression").ToList();
+
+        visitedTypeNames.Should().ContainInOrder(expectedTypeNames);
+        visitedTypeNames.Should().HaveCount(expectedTypeNames.Count);
+    }
+
+    [Fact]
+    public void VisitSparseFieldTable()
+    {
+        // Arrange
+        var parser = new SparseFieldSetParser();
+
+        ResourceType blogType = ResourceGraph.GetResourceType<Blog>();
+        ResourceType commentType = ResourceGraph.GetResourceType<Comment>();
+
+        var sparseFieldTable = new Dictionary<ResourceType, SparseFieldSetExpression>
+        {
+            [blogType] = parser.Parse("title,owner", blogType)!,
+            [commentType] = parser.Parse("text,createdAt", commentType)!
+        };
+
+        var expression = new SparseFieldTableExpression(sparseFieldTable.ToImmutableDictionary());
+        var rewriter = new TestableQueryExpressionRewriter();
+
+        // Act
+        rewriter.Visit(expression, null);
+
+        // Assert
+        List<string> visitedTypeNames = rewriter.ExpressionsVisited.Select(queryExpression => queryExpression.GetType().Name).ToList();
+
+        visitedTypeNames.Should().HaveCount(3);
+        visitedTypeNames[0].Should().Be("SparseFieldTableExpression");
+        visitedTypeNames[1].Should().Be("SparseFieldSetExpression");
+        visitedTypeNames[2].Should().Be("SparseFieldSetExpression");
+    }
+
+    [Theory]
+    [InlineData("any(userName,'A','B')", "Any,ResourceFieldChain,LiteralConstant,LiteralConstant")]
+    [InlineData("equals(userName,null)", "Comparison,ResourceFieldChain,NullConstant")]
+    [InlineData("has(loginAttempts)", "Has,ResourceFieldChain")]
+    [InlineData("has(loginAttempts,equals(isSucceeded,'true'))", "Has,ResourceFieldChain,Comparison,ResourceFieldChain,LiteralConstant")]
+    [InlineData("isType(person,men)", "IsType,ResourceFieldChain")]
+    [InlineData("isType(person,men,greaterThan(age,'18'))", "IsType,ResourceFieldChain,Comparison,ResourceFieldChain,LiteralConstant")]
+    [InlineData("and(equals(userName,null),has(loginAttempts))", "Logical,Comparison,ResourceFieldChain,NullConstant,Has,ResourceFieldChain")]
+    [InlineData("startsWith(userName,'A')", "MatchText,ResourceFieldChain,LiteralConstant")]
+    [InlineData("not(equals(count(loginAttempts),'1'))", "Not,Comparison,Count,ResourceFieldChain,LiteralConstant")]
+    public void VisitFilter(string expressionText, string expectedTypes)
+    {
+        // Arrange
+        var parser = new FilterParser(ResourceFactory);
+        ResourceType webAccountType = ResourceGraph.GetResourceType<WebAccount>();
+
+        QueryExpression expression = parser.Parse(expressionText, webAccountType);
+        var rewriter = new TestableQueryExpressionRewriter();
+
+        // Act
+        rewriter.Visit(expression, null);
+
+        // Assert
+        List<string> visitedTypeNames = rewriter.ExpressionsVisited.Select(queryExpression => queryExpression.GetType().Name).ToList();
+        List<string> expectedTypeNames = expectedTypes.Split(',').Select(type => type + "Expression").ToList();
+
+        visitedTypeNames.Should().ContainInOrder(expectedTypeNames);
+        visitedTypeNames.Should().HaveCount(expectedTypeNames.Count);
+    }
+
+    [Theory]
+    [InlineData("title", "Sort,SortElement,ResourceFieldChain")]
+    [InlineData("title,-platformName", "Sort,SortElement,ResourceFieldChain,SortElement,ResourceFieldChain")]
+    [InlineData("count(posts)", "Sort,SortElement,Count,ResourceFieldChain")]
+    public void VisitSort(string expressionText, string expectedTypes)
+    {
+        // Arrange
+        var parser = new SortParser();
+        ResourceType blogType = ResourceGraph.GetResourceType<Blog>();
+
+        QueryExpression expression = parser.Parse(expressionText, blogType);
+        var rewriter = new TestableQueryExpressionRewriter();
+
+        // Act
+        rewriter.Visit(expression, null);
+
+        // Assert
+        List<string> visitedTypeNames = rewriter.ExpressionsVisited.Select(queryExpression => queryExpression.GetType().Name).ToList();
+        List<string> expectedTypeNames = expectedTypes.Split(',').Select(type => type + "Expression").ToList();
+
+        visitedTypeNames.Should().ContainInOrder(expectedTypeNames);
+        visitedTypeNames.Should().HaveCount(expectedTypeNames.Count);
+    }
+
+    [Theory]
+    [InlineData("2", "PaginationQueryStringValue,PaginationElementQueryStringValue")]
+    [InlineData("posts:3,2", "PaginationQueryStringValue,PaginationElementQueryStringValue,ResourceFieldChain,PaginationElementQueryStringValue")]
+    public void VisitPagination(string expressionText, string expectedTypes)
+    {
+        // Arrange
+        var parser = new PaginationParser();
+        ResourceType blogType = ResourceGraph.GetResourceType<Blog>();
+
+        QueryExpression expression = parser.Parse(expressionText, blogType);
+        var rewriter = new TestableQueryExpressionRewriter();
+
+        // Act
+        rewriter.Visit(expression, null);
+
+        // Assert
+        List<string> visitedTypeNames = rewriter.ExpressionsVisited.Select(queryExpression => queryExpression.GetType().Name).ToList();
+        List<string> expectedTypeNames = expectedTypes.Split(',').Select(type => type + "Expression").ToList();
+
+        visitedTypeNames.Should().ContainInOrder(expectedTypeNames);
+        visitedTypeNames.Should().HaveCount(expectedTypeNames.Count);
+    }
+
+    [Theory]
+    [InlineData("filter", "QueryStringParameterScope,LiteralConstant")]
+    [InlineData("filter[posts.comments]", "QueryStringParameterScope,LiteralConstant,ResourceFieldChain")]
+    public void VisitParameterScope(string expressionText, string expectedTypes)
+    {
+        // Arrange
+        var parser = new QueryStringParameterScopeParser(FieldChainRequirements.EndsInToMany);
+        ResourceType blogType = ResourceGraph.GetResourceType<Blog>();
+
+        QueryExpression expression = parser.Parse(expressionText, blogType);
+        var rewriter = new TestableQueryExpressionRewriter();
+
+        // Act
+        rewriter.Visit(expression, null);
+
+        // Assert
+        List<string> visitedTypeNames = rewriter.ExpressionsVisited.Select(queryExpression => queryExpression.GetType().Name).ToList();
+        List<string> expectedTypeNames = expectedTypes.Split(',').Select(type => type + "Expression").ToList();
+
+        visitedTypeNames.Should().ContainInOrder(expectedTypeNames);
+        visitedTypeNames.Should().HaveCount(expectedTypeNames.Count);
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Queries/TestableQueryExpressionRewriter.cs b/test/JsonApiDotNetCoreTests/UnitTests/Queries/TestableQueryExpressionRewriter.cs
new file mode 100644
index 0000000000..71cd56fc6b
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Queries/TestableQueryExpressionRewriter.cs
@@ -0,0 +1,151 @@
+using JsonApiDotNetCore.Queries.Expressions;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Queries;
+
+internal sealed class TestableQueryExpressionRewriter : QueryExpressionRewriter<object?>
+{
+    public List<QueryExpression> ExpressionsVisited { get; } = new();
+
+    public override QueryExpression DefaultVisit(QueryExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.DefaultVisit(expression, argument);
+    }
+
+    public override QueryExpression? VisitComparison(ComparisonExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitComparison(expression, argument);
+    }
+
+    public override QueryExpression? VisitResourceFieldChain(ResourceFieldChainExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitResourceFieldChain(expression, argument);
+    }
+
+    public override QueryExpression VisitLiteralConstant(LiteralConstantExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitLiteralConstant(expression, argument);
+    }
+
+    public override QueryExpression VisitNullConstant(NullConstantExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitNullConstant(expression, argument);
+    }
+
+    public override QueryExpression? VisitLogical(LogicalExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitLogical(expression, argument);
+    }
+
+    public override QueryExpression? VisitNot(NotExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitNot(expression, argument);
+    }
+
+    public override QueryExpression? VisitHas(HasExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitHas(expression, argument);
+    }
+
+    public override QueryExpression VisitIsType(IsTypeExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitIsType(expression, argument);
+    }
+
+    public override QueryExpression? VisitSortElement(SortElementExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitSortElement(expression, argument);
+    }
+
+    public override QueryExpression? VisitSort(SortExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitSort(expression, argument);
+    }
+
+    public override QueryExpression VisitPagination(PaginationExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitPagination(expression, argument);
+    }
+
+    public override QueryExpression? VisitCount(CountExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitCount(expression, argument);
+    }
+
+    public override QueryExpression? VisitMatchText(MatchTextExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitMatchText(expression, argument);
+    }
+
+    public override QueryExpression? VisitAny(AnyExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitAny(expression, argument);
+    }
+
+    public override QueryExpression? VisitSparseFieldTable(SparseFieldTableExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitSparseFieldTable(expression, argument);
+    }
+
+    public override QueryExpression VisitSparseFieldSet(SparseFieldSetExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitSparseFieldSet(expression, argument);
+    }
+
+    public override QueryExpression? VisitQueryStringParameterScope(QueryStringParameterScopeExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitQueryStringParameterScope(expression, argument);
+    }
+
+    public override QueryExpression PaginationQueryStringValue(PaginationQueryStringValueExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.PaginationQueryStringValue(expression, argument);
+    }
+
+    public override QueryExpression PaginationElementQueryStringValue(PaginationElementQueryStringValueExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.PaginationElementQueryStringValue(expression, argument);
+    }
+
+    public override QueryExpression VisitInclude(IncludeExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitInclude(expression, argument);
+    }
+
+    public override QueryExpression VisitIncludeElement(IncludeElementExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitIncludeElement(expression, argument);
+    }
+
+    public override QueryExpression VisitQueryableHandler(QueryableHandlerExpression expression, object? argument)
+    {
+        Capture(expression);
+        return base.VisitQueryableHandler(expression, argument);
+    }
+
+    private void Capture(QueryExpression expression)
+    {
+        ExpressionsVisited.Add(expression);
+    }
+}

From b40f3f390684609e1dd5b96a571927079fc79f10 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Fri, 1 Apr 2022 15:09:03 +0200
Subject: [PATCH 17/19] Exclude example project from code coverage

---
 src/Examples/JsonApiDotNetCoreExample/Program.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Examples/JsonApiDotNetCoreExample/Program.cs b/src/Examples/JsonApiDotNetCoreExample/Program.cs
index 482e42cdf7..bda826d131 100644
--- a/src/Examples/JsonApiDotNetCoreExample/Program.cs
+++ b/src/Examples/JsonApiDotNetCoreExample/Program.cs
@@ -1,3 +1,4 @@
+using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Serialization;
 using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Diagnostics;
@@ -6,6 +7,8 @@
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 
+[assembly: ExcludeFromCodeCoverage]
+
 WebApplication app = CreateWebApplication(args);
 
 await CreateDatabaseAsync(app.Services);

From 364e641069be483ae61a76595c712f0a03b838b7 Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Fri, 1 Apr 2022 19:12:02 +0200
Subject: [PATCH 18/19] Review feedback

---
 JsonApiDotNetCore.sln.DotSettings             |  1 +
 docs/usage/reading/filtering.md               |  3 ++-
 docs/usage/resources/inheritance.md           |  5 +++--
 .../Services/JsonApiResourceService.cs        | 20 +++++++++----------
 4 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/JsonApiDotNetCore.sln.DotSettings b/JsonApiDotNetCore.sln.DotSettings
index c4f0d3d36d..2a7eb28d9b 100644
--- a/JsonApiDotNetCore.sln.DotSettings
+++ b/JsonApiDotNetCore.sln.DotSettings
@@ -629,6 +629,7 @@ $left$ = $right$;</s:String>
 	<s:String x:Key="/Default/PatternsAndTemplates/StructuralSearch/Pattern/=B3D9EE6B4EC62A4F961EB15F9ADEC2C6/ReplacePattern/@EntryValue">$collection$.IsNullOrEmpty()</s:String>
 	<s:String x:Key="/Default/PatternsAndTemplates/StructuralSearch/Pattern/=B3D9EE6B4EC62A4F961EB15F9ADEC2C6/SearchPattern/@EntryValue">$collection$ == null || !$collection$.Any()</s:String>
 	<s:String x:Key="/Default/PatternsAndTemplates/StructuralSearch/Pattern/=B3D9EE6B4EC62A4F961EB15F9ADEC2C6/Severity/@EntryValue">WARNING</s:String>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=Accurize/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=appsettings/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Assignee/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Contoso/@EntryIndexedValue">True</s:Boolean>
diff --git a/docs/usage/reading/filtering.md b/docs/usage/reading/filtering.md
index 285f3b5a98..a1c1215ccd 100644
--- a/docs/usage/reading/filtering.md
+++ b/docs/usage/reading/filtering.md
@@ -90,7 +90,6 @@ Which returns only customers that have at least one unpaid order.
 _since v5.0_
 
 Use the `isType` filter function to perform a type check on a derived type. You can pass a nested filter, where the derived fields are accessible.
-The first parameter can be used to perform the type check on a to-one relationship path.
 
 Only return men:
 ```http
@@ -102,6 +101,8 @@ Only return men with beards:
 GET /humans?filter=isType(,men,equals(hasBeard,'true')) HTTP/1.1
 ```
 
+The first parameter of `isType` can be used to perform the type check on a to-one relationship path.
+
 Only return people whose best friend is a man with children:
 ```http
 GET /humans?filter=isType(bestFriend,men,has(children)) HTTP/1.1
diff --git a/docs/usage/resources/inheritance.md b/docs/usage/resources/inheritance.md
index 864a38bea1..47cf85ca67 100644
--- a/docs/usage/resources/inheritance.md
+++ b/docs/usage/resources/inheritance.md
@@ -185,7 +185,6 @@ public override SortExpression OnApplySort(SortExpression? existingSort)
 ### Filtering
 
 Use the `isType` filter function to perform a type check on a derived type. You can pass a nested filter, where the derived fields are accessible.
-The first parameter can be used to perform the type check on a to-one relationship path.
 
 Only return men:
 ```http
@@ -197,6 +196,8 @@ Only return men with beards:
 GET /humans?filter=isType(,men,equals(hasBeard,'true')) HTTP/1.1
 ```
 
+The first parameter of `isType` can be used to perform the type check on a to-one relationship path.
+
 Only return people whose best friend is a man with children:
 ```http
 GET /humans?filter=isType(bestFriend,men,has(children)) HTTP/1.1
@@ -287,7 +288,7 @@ Resource definitions provide a better solution, see below.
 
 ### Resource definitions
 
-In contract to the request pipeline, JsonApiDotNetCore always executes the resource definition that matches the *stored* type.
+In contrast to the request pipeline, JsonApiDotNetCore always executes the resource definition that matches the *stored* type.
 This enables to implement business logic in a central place, irrespective of which endpoint was used or whether base types were used in relationships.
 
 To delegate logic for base types to their matching resource type, you can build a chain of resource definitions. And because you'll always get the
diff --git a/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs b/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs
index 74733f6895..540ee5b73b 100644
--- a/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs
+++ b/src/JsonApiDotNetCore/Services/JsonApiResourceService.cs
@@ -202,11 +202,11 @@ private async Task RetrieveResourceCountForNonPrimaryEndpointAsync(TId id, HasMa
         TResource resourceFromRequest = resource;
         _resourceChangeTracker.SetRequestAttributeValues(resourceFromRequest);
 
-        await RefreshResourceTypesInHierarchyToAssignInRelationshipsAsync(resourceFromRequest, cancellationToken);
+        await AccurizeResourceTypesInHierarchyToAssignInRelationshipsAsync(resourceFromRequest, cancellationToken);
 
         Type resourceClrType = resourceFromRequest.GetClrType();
         TResource resourceForDatabase = await _repositoryAccessor.GetForCreateAsync<TResource, TId>(resourceClrType, resourceFromRequest.Id, cancellationToken);
-        PromoteJsonApiRequest(resourceForDatabase);
+        AccurizeJsonApiRequest(resourceForDatabase);
 
         _resourceChangeTracker.SetInitiallyStoredAttributeValues(resourceForDatabase);
 
@@ -249,7 +249,7 @@ protected virtual async Task InitializeResourceAsync(TResource resourceForDataba
         await _resourceDefinitionAccessor.OnPrepareWriteAsync(resourceForDatabase, WriteOperationKind.CreateResource, cancellationToken);
     }
 
-    private async Task RefreshResourceTypesInHierarchyToAssignInRelationshipsAsync(TResource primaryResource, CancellationToken cancellationToken)
+    private async Task AccurizeResourceTypesInHierarchyToAssignInRelationshipsAsync(TResource primaryResource, CancellationToken cancellationToken)
     {
         await ValidateResourcesToAssignInRelationshipsExistWithRefreshAsync(primaryResource, true, cancellationToken);
     }
@@ -360,7 +360,7 @@ public virtual async Task AddToToManyRelationshipAsync(TId leftId, string relati
             // The left resource may be stored as a derived type. We fetch it, so we'll know the stored type, which
             // enables to invoke IResourceDefinition<TResource> with TResource being the stored resource type.
             resourceFromDatabase ??= await GetPrimaryResourceForUpdateAsync(leftId, cancellationToken);
-            PromoteJsonApiRequest(resourceFromDatabase);
+            AccurizeJsonApiRequest(resourceFromDatabase);
         }
 
         ISet<IIdentifiable> effectiveRightResourceIds = rightResourceIds;
@@ -453,10 +453,10 @@ private async Task<TResource> GetForHasManyUpdateAsync(HasManyAttribute hasManyR
         TResource resourceFromRequest = resource;
         _resourceChangeTracker.SetRequestAttributeValues(resourceFromRequest);
 
-        await RefreshResourceTypesInHierarchyToAssignInRelationshipsAsync(resourceFromRequest, cancellationToken);
+        await AccurizeResourceTypesInHierarchyToAssignInRelationshipsAsync(resourceFromRequest, cancellationToken);
 
         TResource resourceFromDatabase = await GetPrimaryResourceForUpdateAsync(id, cancellationToken);
-        PromoteJsonApiRequest(resourceFromDatabase);
+        AccurizeJsonApiRequest(resourceFromDatabase);
 
         _resourceChangeTracker.SetInitiallyStoredAttributeValues(resourceFromDatabase);
 
@@ -503,7 +503,7 @@ public virtual async Task SetRelationshipAsync(TId leftId, string relationshipNa
             : rightValue;
 
         TResource resourceFromDatabase = await GetPrimaryResourceForUpdateAsync(leftId, cancellationToken);
-        PromoteJsonApiRequest(resourceFromDatabase);
+        AccurizeJsonApiRequest(resourceFromDatabase);
 
         await _resourceDefinitionAccessor.OnPrepareWriteAsync(resourceFromDatabase, WriteOperationKind.SetRelationship, cancellationToken);
 
@@ -537,7 +537,7 @@ public virtual async Task DeleteAsync(TId id, CancellationToken cancellationToke
             // The resource to delete may be stored as a derived type. We fetch it, so we'll know the stored type, which
             // enables to invoke IResourceDefinition<TResource> with TResource being the stored resource type.
             resourceFromDatabase = await GetPrimaryResourceForUpdateAsync(id, cancellationToken);
-            PromoteJsonApiRequest(resourceFromDatabase);
+            AccurizeJsonApiRequest(resourceFromDatabase);
         }
 
         try
@@ -571,7 +571,7 @@ public virtual async Task RemoveFromToManyRelationshipAsync(TId leftId, string r
         var hasManyRelationship = (HasManyAttribute)_request.Relationship;
 
         TResource resourceFromDatabase = await GetForHasManyUpdateAsync(hasManyRelationship, leftId, rightResourceIds, cancellationToken);
-        PromoteJsonApiRequest(resourceFromDatabase);
+        AccurizeJsonApiRequest(resourceFromDatabase);
 
         object? rightValue = await AssertRightResourcesExistAsync(rightResourceIds, cancellationToken);
         ISet<IIdentifiable> effectiveRightResourceIds = ((IEnumerable<IIdentifiable>)rightValue!).ToHashSet(IdentifiableComparer.Instance);
@@ -610,7 +610,7 @@ protected async Task<TResource> GetPrimaryResourceForUpdateAsync(TId id, Cancell
         return resource;
     }
 
-    private void PromoteJsonApiRequest(TResource resourceFromDatabase)
+    private void AccurizeJsonApiRequest(TResource resourceFromDatabase)
     {
         // When using resource inheritance, the stored left-side resource may be more derived than what this endpoint assumes.
         // In that case, we promote data in IJsonApiRequest to better represent what is going on.

From 3a1665caa6bc452ed5627077abead475bf8f86bc Mon Sep 17 00:00:00 2001
From: Bart Koelman <bart@degreed.com>
Date: Mon, 4 Apr 2022 09:57:58 +0200
Subject: [PATCH 19/19] Update ROADMAP.md

---
 ROADMAP.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ROADMAP.md b/ROADMAP.md
index 559e0bfe7d..c3baab5443 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -27,13 +27,13 @@ The need for breaking changes has blocked several efforts in the v4.x release, s
 - [x] Auto-generated controllers [#732](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/732) [#365](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/365)
 - [x] Support .NET 6 with EF Core 6 [#1109](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/1109)
 - [x] Extract annotations into separate package [#730](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/730)
+- [x] Resource inheritance [#844](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/844)
 
 Aside from the list above, we have interest in the following topics. It's too soon yet to decide whether they'll make it into v5.x or in a later major version.
 
 - Optimistic concurrency [#1004](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/1004)
 - OpenAPI (Swagger) [#1046](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/1046)
 - Fluent API [#776](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/776)
-- Resource inheritance [#844](https://github.com/json-api-dotnet/JsonApiDotNetCore/issues/844)
 - Idempotency
 
 ## Feedback