The Standard — Versioning

What this skill is

This skill defines the required versioning approach for:

release versioning
file versioning (models, services, exceptions)
API versioning
deprecation signaling
discovery capabilities

This skill MUST follow the explicit versioning model defined here and MUST NOT substitute alternative semantic versioning strategies, compatibility theories, or inferred conventions.

The skill exists to keep version changes:

explicit
structured
non-destructive
discoverable
safe for consumers

When to use

Use this skill whenever:

creating a new release version
introducing a model change that requires versioning
introducing a service or routine change that requires versioning
creating new versioned files or folders
defining API routes for versioned resources
marking code or APIs as deprecated
implementing discovery capabilities
reviewing version-related changes in PRs

Explicit coverage map

This skill covers these primary areas:

Release versioning
Code versioning
Deprecation
Discovery capabilities

Code versioning in this skill includes:

file versioning
API versioning
deprecation markers
discovery capability signaling that helps consumers understand supported behavior

Release Versioning

Release Format

Release versions MUST use the following exact format:

v1.2.3.4

Segment Meaning

Segment	Meaning
1	Model change
2	Service or routine change
3	Bug fix or configuration change
4	Automated build version

These meanings are fixed for this skill and MUST NOT be reinterpreted.

Release Increment Rules

A release version MUST remain in the exact v1.2.3.4 shape.
A model change MUST increment segment 1 and MUST reset segments 2, 3, and 4 to zero.
A service or routine change MUST increment segment 2 and MUST reset segments 3 and 4 to zero.
A bug fix or configuration change MUST increment segment 3 and MUST reset segment 4 to zero.
A new automated build for the same code MUST increment segment 4 only.
If multiple change types occur together, the highest-order change MUST win and all lower segments MUST reset to zero.

Release Examples

Given current version:

v1.2.3.4

Expected next versions:

model change → v2.0.0.0
service or routine change → v1.3.0.0
bug fix or configuration change → v1.2.4.0
automated build of the same code → v1.2.3.5
model + service change together → v2.0.0.0

Release Guidance

Use the release version to describe what kind of change happened, not merely that a change happened.

That means:

a model change is never hidden inside the service segment
a service change is never hidden inside the bug/config segment
a build increment is never used to represent code change

File Versioning

V0 Convention

A file without a version folder is treated as V0.

Examples:

Models/Foundations/Students/Student.cs
Services/Foundations/Students/StudentService.cs
Models/Foundations/Students/Exceptions/

This means the starting shape is unversioned on disk, but version zero is still logically assumed.

Model Changes

When a model changes, a new versioned file MUST be created under a version folder that is a subfolder of the original location.

Example:

Models/Foundations/Students/V1/StudentV1.cs

This pattern means:

the original V0 model remains where it is
the new model version lives in a nested V1 folder
the version number becomes explicit in both folder and type name

Model-Driven Service Changes

When a model changes, the corresponding service MUST also be versioned under the same model version folder.

Example:

Services/Foundations/Students/V1/StudentV1Service.cs

Related exceptions MUST align with the matching versioned model path.

Example:

Models/Foundations/Students/V1/Exceptions/

Service Behavior Versioning

When the behavior of a service changes without any change to the underlying model, the service file is versioned to reflect that behavioral evolution. Behavior changes include modifying validation rules, making a previously optional field required, or altering business logic.

If the model is still at V0 and only the service behavior changes, the versioned service file is placed at the service location root with a behavior version suffix — no version folder is created:

Services/Foundations/Students/StudentServiceV1.cs

If the model has already been versioned (e.g., V1) and the service behavior changes, the versioned service file is placed inside the model's version folder with both the model version and the behavior version in the name:

Services/Foundations/Students/V1/StudentV1ServiceV1.cs

Combined Model and Behavior Changes

When both the model and the service behavior change together in the same release, only the model version increments. The behavior version resets to V0, implied by its absence from the file name. A new model always means new service behavior by definition, so the behavior version returns to its baseline:

Services/Foundations/Students/V2/StudentV2Service.cs

The behavior version suffix is absent, signaling that the behavior version is V0 for this new model version. The cycle can then repeat as further behavior changes are introduced.

File Rules

No version folder means V0 is implied.
A new version MUST be introduced by creating new versioned files and folders, not by overwriting the earlier implementation.
A model change MUST produce a versioned model file under a Vn subfolder.
A model change MUST produce a versioned service file under the matching Vn subfolder. A service behavior-only change MUST produce a versioned service file at the service location root using the behavior version as a suffix — no new version folder is created.
Versioned exceptions MUST live beneath the corresponding versioned model path.
Existing earlier-version code MUST remain available unless there is an explicit deprecation/removal strategy outside the introduction of the new version.

Naming Convention

Versioned file/type naming MUST follow this pattern:

model → {Entity}V{n}.cs
service with model version only → {Entity}V{n}Service.cs
service with behavior version only → {Entity}ServiceV{n}.cs
service with both model and behavior versions → {Entity}V{m}ServiceV{n}.cs

The behavior version always appears as a suffix after the service name. When both a model change and a behavior change occur in the same release, the behavior version resets to V0 and is implied by its absence from the file name.

Scenario	Example file name
Model V1, no behavior version	`StudentV1Service.cs`
No model version, behavior V1	`StudentServiceV1.cs`
Model V1, behavior V1	`StudentV1ServiceV1.cs`
Model V2 introduced (behavior resets to V0)	`StudentV2Service.cs`

API Versioning

Default API Route

The initial API is exposed without a version prefix:

api/Students

This is the route for V0.

Model Version Route

If the model changes, the route MUST surface the model version:

api/V1/Students

Here, V1 tells the consumer that this endpoint represents the version 1 model.

Service Behavior Route

If the model is already at version 1 and the service behavior changes for that model, the route MUST surface both the model version and the behavior version:

api/V1.1/Students

In this shape:

1 before the dot denotes the model version
1 after the dot denotes the behavior/service version

This is a model + behavior pairing and MUST be interpreted that way.

If only behaviour changed but the model stayed the same, the new route will be api/V0.1/Students — the model version is still 0, but the behavior version has incremented to 1.

API Rules

api/{resource} denotes V0.
api/Vn/{resource} denotes model version n.
api/Vn.m/{resource} denotes model version n with behavior version m.
A route version MUST communicate the intended model and behavior pairing.
The API route MUST remain aligned with the versioning story of the underlying model/service pair.

API Example Flow

Starting point:

api/Students

After model change:

api/V1/Students

After additional service behavior change for the V1 model:

api/V1.1/Students

Deprecation

Deprecation MUST be clear enough that consumers can see:

that an API is deprecated
when it is expected to sunset
where to go for migration guidance

Consumers MUST be given enough time to act before the deprecated version is sunset.

Deprecation Signaling

A valid approach is to surface deprecation metadata through headers or attributes that emit those headers.

Example using a controller action attribute:

[ApiController]
[Route("api/[controller]")]
public class SampleController : ControllerBase
{
    [HttpGet]
    [DeprecatedApi(
        Sunset = "2024-12-31",
        Warning = "This API is deprecated. Please migrate to v2.",
        Link = "https://example.com/deprecation-info")]
    public IActionResult GetSampleData()
    {
        return Ok(new { message = "Sample data" });
    }
}

Key Libraries

Package	Purpose
`Attrify`	A NuGet library for controlling API visibility and lifecycle (e.g. deprecation) through attributes applied to controllers and actions

Code Deprecation

Code that is no longer maintained or supported SHOULD be marked with:

[Obsolete("This version is deprecated and no longer maintained.")]

Use the obsolete marker to make deprecation visible to maintainers and consumers at compile time.

Capabilities

Capabilities are recommended so consumers can discover what is supported in each version before invoking a feature.

This is especially useful where model versions and service behaviors differ by version or by provider.

Capability Goals

A capabilities surface should help consumers discover:

what features are supported
what model versions are supported
what behavior versions are supported
what optional features are unavailable

Capability Surface Options

Capabilities MAY be exposed through:

Swagger
middleware-based metadata
a bespoke capabilities endpoint
a provider-specific capabilities endpoint

Provider Example

In a provider-based architecture such as a SPAL provider, each concrete provider can expose a capabilities endpoint that tells consumers which operations are supported.

This pattern allows consumers to safely determine whether a provider supports a given operation before invoking it, avoiding runtime failures.

1. Operation Attribute

[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public sealed class StudentOperationAttribute : Attribute
{
    public string OperationName { get; }

    public StudentOperationAttribute(string operationName) =>
        OperationName = operationName ?? string.Empty;

    public StudentOperationAttribute() =>
        OperationName = string.Empty;
}

2. Capabilities Models

public sealed class ResourceCapabilities
{
    public string ResourceName { get; init; } = string.Empty;
    public IReadOnlyCollection<string> SupportedOperations { get; init; } =
        Array.Empty<string>();
}

public sealed class ProviderCapabilities
{
    public string ProviderName { get; init; } = string.Empty;
    public IReadOnlyCollection<ResourceCapabilities> SupportedResources { get; init; } =
        Array.Empty<ResourceCapabilities>();
}

3. Student Provider Contract

public interface IStudentProvider
{
    string ProviderName { get; }

    ProviderCapabilities Capabilities { get; }

    IStudentResource Students { get; }
}

4. Resource Contract

public interface IStudentResource
{
    ValueTask<Student> AddAsync(Student student);
}

5. Provider Base (Simplified Capability Declaration)

public abstract class StudentProviderBase : IStudentProvider
{
    public abstract string ProviderName { get; }

    public abstract IStudentResource Students { get; }

    public virtual ProviderCapabilities Capabilities =>
        new ProviderCapabilities
        {
            ProviderName = ProviderName,
            SupportedResources = new[]
            {
                new ResourceCapabilities
                {
                    ResourceName = "Student",
                    SupportedOperations = GetSupportedOperations(Students)
                }
            }
        };

    private static IReadOnlyCollection<string> GetSupportedOperations(object resource)
    {
        if (resource is null)
            return Array.Empty<string>();

        return resource.GetType()
            .GetMethods()
            .Select(method =>
                method.GetCustomAttributes(typeof(StudentOperationAttribute), true)
                      .FirstOrDefault() as StudentOperationAttribute)
            .Where(attribute => attribute is not null)
            .Select(attribute => attribute!.OperationName)
            .Where(name => !string.IsNullOrWhiteSpace(name))
            .Distinct()
            .ToArray();
    }
}

6. Example Implementation

public sealed class StudentResource : IStudentResource
{
    [StudentOperation("Add")]
    public ValueTask<Student> AddAsync(Student student)
    {
        return ValueTask.FromResult(student);
    }
}

public sealed class StudentProvider : StudentProviderBase
{
    public override string ProviderName => "DefaultStudentProvider";
    public override IStudentResource Students { get; } = new StudentResource();
}

7. Capability Check Extension

public static class StudentProviderCapabilitiesExtensions
{
    public static bool SupportsOperation(
        this IStudentProvider provider,
        string resourceName,
        string operationName)
    {
        var resource = provider.Capabilities.SupportedResources
            .FirstOrDefault(r => r.ResourceName == resourceName);

        if (resource is null)
            return false;

        return resource.SupportedOperations.Contains(operationName);
    }
}

8. Usage

IStudentProvider provider = new StudentProvider();

if (!provider.SupportsOperation("Student", "Add"))
{
    // avoid call
    return;
}

await provider.Students.AddAsync(new Student());

Key Principle

Capabilities turn runtime uncertainty into a deterministic check:

Without capabilities → call → fail → handle exception
With capabilities → check → decide → call safely

This aligns with the Standard principle:

Avoid invalid operations rather than reacting to them

The Standard Versioning

The Standard — Versioning

What this skill is

When to use

Explicit coverage map

Release Versioning

Release Format

Segment Meaning

Release Increment Rules

Release Examples

Release Guidance

File Versioning

V0 Convention

Model Changes

Model-Driven Service Changes

Service Behavior Versioning

Combined Model and Behavior Changes

File Rules

Naming Convention

API Versioning

Default API Route

Model Version Route

Service Behavior Route

API Rules

API Example Flow

Deprecation

Deprecation Signaling

Key Libraries

Code Deprecation

Capabilities

Capability Goals

Capability Surface Options

Provider Example

1. Operation Attribute

2. Capabilities Models

3. Student Provider Contract

4. Resource Contract

5. Provider Base (Simplified Capability Declaration)

6. Example Implementation

7. Capability Check Extension

8. Usage

Key Principle