Entity Model

Instructions

Create or update the entity model at docs/entity_model.md based on docs/requirements.md. The document contains an ER diagram and attribute tables.

DO NOT

• Add attributes/columns to the Mermaid diagram
• Write prose descriptions like "Key attributes: name, email..."
• Create a "Relationships" table
• Skip the attribute tables

Document Structure

# Entity Model

## Entity Relationship Diagram

```mermaid
erDiagram
    ROOM_TYPE ||--o{ ROOM : "categorizes"
    GUEST ||--o{ RESERVATION : "makes"

ENTITY_NAME

One sentence describing the entity.

| Attribute | Description | Data Type | Length/Precision | Validation Rules | |-----------|-------------|-----------|------------------|-----------------------| | id | ... | Long | 19 | Primary Key, Sequence | | ... | ... | ... | ... | ... |

Required Format for Each Entity

Every entity MUST have:

1. A ### heading with ENTITY_NAME
2. One sentence description
3. An attribute table with exactly 5 columns

Example Entity

ROOM_TYPE

Defines categories of rooms with shared characteristics.

| Attribute | Description | Data Type | Length/Precision | Validation Rules | |-------------|--------------------------|-----------|------------------|---------------------------| | id | Unique identifier | Long | 19 | Primary Key, Sequence | | name | Name of the room type | String | 50 | Not Null, Unique | | description | Detailed description | String | 500 | Optional | | capacity | Maximum number of guests | Integer | 10 | Not Null, Min: 1, Max: 10 | | price | Price per night in CHF | Decimal | 10,2 | Not Null, Min: 0 |

Mermaid Diagram Rules

• Show entity names and relationships ONLY
• NO attributes inside entity blocks
• Use relationship syntax: ENTITY_A ||--o{ ENTITY_B : "relationship"

Validation Rules Reference

Use these values in the "Validation Rules" column (never leave empty):

| Attribute Type | Validation Rules Value | |----------------|----------------------------------| | Primary key | Primary Key, Sequence | | Required field | Not Null | | Unique field | Not Null, Unique | | Foreign key | Not Null, Foreign Key (TABLE.id) | | Optional field | Optional | | With range | Not Null, Min: X, Max: Y | | With values | Not Null, Values: A, B, C | | Email | Not Null, Format: Email |

Data Types Reference

| Data Type | Length/Precision | Usage | |-----------|------------------|-----------------------| | Long | 19 | IDs, foreign keys | | String | varies (50-500) | Text fields | | Integer | 10 | Whole numbers | | Decimal | 10,2 | Currency, percentages | | Boolean | 1 | True/false flags | | Date | - | Date only | | DateTime | - | Date and time |

Multi-Column Constraints

If validation spans multiple columns, add after the table:

Constraints: Check-out date must be after check-in date.

Workflow

1. Read the requirements document
2. Use TodoWrite to create a task for each entity
3. Write the document header and ER diagram (relationships only)
4. For each entity:
   • Write ### heading
   • Write one sentence description
   • Write attribute table with 5 columns
   • Add constraints if needed
   • Mark todo complete
5. Validate the document:
   • Every entity in the ER diagram has a corresponding attribute table section
   • Every attribute table has exactly 5 columns
   • No attributes appear inside the Mermaid diagram entity blocks
   • All foreign keys reference existing entities
   • All validation rules use values from the Validation Rules Reference