# Rule 48: Class Files Must Not Define Inline Slots

🚨 **CRITICAL**: LinkML class files in `schemas/20251121/linkml/modules/classes/` MUST NOT define their own slots inline. All slots MUST be imported from the centralized `modules/slots/` directory.

## Problem Statement

When class files define their own slots (e.g., `AccessRestriction.yaml` defining its own slot properties), this creates:

1. **Duplication**: Same slot semantics defined in multiple places
2. **Inconsistency**: Slot definitions may diverge between files
3. **Frontend Issues**: LinkML viewer cannot properly render slot relationships
4. **Maintenance Burden**: Changes require updates in multiple locations

## Architecture Requirement

```
schemas/20251121/linkml/
├── modules/
│   ├── classes/           # Class definitions ONLY
│   │   └── *.yaml         # NO inline slot definitions
│   ├── slots/             # ALL slot definitions go here
│   │   └── *.yaml         # One file per slot or logical group
│   └── enums/             # Enumeration definitions
```

## Correct Pattern

**Class file** (`modules/classes/AccessRestriction.yaml`):

```yaml
id: https://nde.nl/ontology/hc/class/AccessRestriction
name: AccessRestriction
prefixes:
  hc: https://nde.nl/ontology/hc/
  linkml: https://w3id.org/linkml/

imports:
  - linkml:types
  - ../slots/restriction_type      # Import slot from centralized location
  - ../slots/restriction_reason
  - ../slots/applies_from
  - ../slots/applies_until

default_range: string

classes:
  AccessRestriction:
    class_uri: hc:AccessRestriction
    description: >-
      Describes access restrictions on heritage collections or items.
    slots:
      - restriction_type           # Reference slot by name
      - restriction_reason
      - applies_from
      - applies_until
```

**Slot file** (`modules/slots/restriction_type.yaml`):

```yaml
id: https://nde.nl/ontology/hc/slot/restriction_type
name: restriction_type
prefixes:
  hc: https://nde.nl/ontology/hc/
  schema: http://schema.org/
  linkml: https://w3id.org/linkml/

imports:
  - linkml:types

slots:
  restriction_type:
    slot_uri: hc:restrictionType
    description: The type of access restriction applied.
    range: string
    exact_mappings:
      - schema:accessMode
```

## Anti-Pattern (WRONG)

**DO NOT** define slots inline in class files:

```yaml
# WRONG - AccessRestriction.yaml with inline slots
classes:
  AccessRestriction:
    slots:
      - restriction_type
      
slots:                           # ❌ DO NOT define slots here
  restriction_type:
    description: Type of restriction
    range: string
```

## Identifying Violations

To find class files that incorrectly define slots:

```bash
# Find class files with inline slot definitions
grep -l "^slots:" schemas/20251121/linkml/modules/classes/*.yaml
```

Files that match need refactoring:
1. Extract slot definitions to `modules/slots/`
2. Add imports for the extracted slots
3. Remove inline `slots:` section from class file

## Known Violations to Fix

The following class files have been identified as defining their own slots and require refactoring:

- `AccessRestriction.yaml` - visible at https://nde.nl/ontology/hc/class/AccessRestriction
- (Add others as discovered)

## Migration Workflow

1. **Identify inline slots** in class file
2. **Check if slot exists** in `modules/slots/`
3. **If exists**: Remove inline definition, add import
4. **If not exists**: Create new slot file in `modules/slots/`, then add import
5. **Validate**: Run `linkml-validate` to ensure schema integrity
6. **Update manifest**: Regenerate `manifest.json` if needed

## Rationale

- **Single Source of Truth**: Each slot defined exactly once
- **Reusability**: Slots can be used across multiple classes
- **Frontend Compatibility**: LinkML viewer depends on centralized slots for proper edge rendering in UML diagrams
- **Semantic Consistency**: `slot_uri` and mappings defined once, applied everywhere
- **Maintenance**: Changes to slot semantics applied in one place

## See Also

- Rule 38: Slot Centralization and Semantic URI Requirements
- Rule: Slot Naming Convention (Current Style)
- Rule 42: No Ontology Prefixes in Slot Names
- Rule 43: Slot Nouns Must Be Singular