# Content Classes

Date: 2026-05-04

## Purpose

Content classes are data-defined composition rules for reusable document
structures, overlays, and variants. They are not Python inheritance. They are a
deterministic way to combine slots such as sections, assertions, snippets,
processors, and style guidance.

This is the P10.7 resolver spike for future class/object-style workflows.

## Model

A class can declare:

- `extends`: parent classes
- `slots`: structured values to contribute
- `merge_policies`: per-slot merge behavior

Example:

```yaml
classes:
  base-prd:
    slots:
      sections:
        - Problem
        - Decision
  enterprise:
    extends:
      - base-prd
    slots:
      sections:
        - Compliance
    merge_policies:
      sections: append
```

## Linearization

Multiple inheritance uses a C3-style linearization. That gives us:

- deterministic parent ordering
- monotonic inheritance behavior
- explicit diagnostics for cycles, unknown parents, and inconsistent precedence

The resolved class is merged from base to leaf according to the computed
linearization.

## Merge Policies

Initial policies:

- `replace`
- `append`
- `prepend`
- `deep_merge`
- `error_on_conflict`

Unknown policies and invalid value shapes produce diagnostics.

## CLI

Resolve a class:

```bash
mkt class resolve examples/classes/prd-classes.yaml enterprise-prd
```

JSON/YAML output includes the linearization, merged slots, and diagnostics.

## Extension Boundary

The current resolver does not yet instantiate Markdown documents or inject
snippets. It establishes the deterministic inheritance and merge floor. Later
work can connect resolved slots to contracts, references, processors, and
generation plans.