Data Model Creation

Activation Contract

Use this first when

• The user explicitly wants Mermaid classDiagram modeling.
• The task needs complex multi-entity relational design, visual ER-style output, or generated data-model structure rather than direct SQL.
• You need to create or update CloudBase data models through the dedicated modeling tools.

Read before writing code if

• The request mentions data model, ER diagram, Mermaid, relationship graph, or enterprise schema design.
• The user wants to reuse or update an existing published model.

Then also read

• Direct SQL creation or schema change -> ../relational-database-tool/SKILL.md
• Broader feature planning before schema work -> ../spec-workflow/SKILL.md

Do NOT use for

• Simple CREATE TABLE, ALTER TABLE, or CRUD tasks.
• Document-database collection design.
• Frontend-only data-shape discussions with no modeling requirement.

Common mistakes / gotchas

• Using Mermaid modeling for a task that only needs one or two SQL statements.
• Mixing SQL-table design and NoSQL collection design in the same model.
• Generating diagrams without first deciding entity boundaries and ownership relations.
• Publishing a new model before validating the generated fields and relationships.

Minimal checklist

• Confirm Mermaid modeling is actually needed.
• List the core entities and relationships first.
• Decide whether this is a new model or an update.
• Keep the initial model small unless the user explicitly wants a large enterprise schema.

Overview

This skill is an advanced modeling path, not the default path for database work.

• For most database tasks, use relational-database-tool and write SQL directly.
• Use this skill only when diagram-driven modeling adds value.

Quick routing

Use relational-database-tool instead when

• You need CREATE TABLE, ALTER TABLE, INSERT, UPDATE, DELETE, or SELECT
• The schema is small and already clear
• The user never asked for a visual model

Use this skill when

• You need multi-entity relationship modeling
• You need Mermaid classDiagram output
• You want generated model structure and documentation
• You need a clean modeling pass before SQL implementation

How to use this skill (for a coding agent)

1. Clarify the entity set

   • Extract business entities, ownership, and relationship cardinality from the request.
   • Prefer 3-5 core entities unless the user clearly asks for more.

2. Model first, then generate

   • Draft Mermaid classDiagram content.
   • Validate names, field types, and relationships before calling modeling tools.

3. Use the right tools

   • Read/list existing models -> manageDataModel(action="list"|"get"|"docs")
   • Create or update a model -> modifyDataModel

4. Publish carefully

   • Prefer creating with unpublished or draft-like intent first.
   • Publish only after checking field names, required constraints, and relationship directions.

Mermaid generation rules

Naming

• Class names -> PascalCase
• Field names -> camelCase
• Convert Chinese business descriptions into clear English identifiers
• Keep enum values human-readable when needed

Type mapping

Required structure conventions

• Use required() only for fields the user explicitly marks as required.
• Use unique() only for explicit uniqueness needs.
• Use display_field() for the human-facing label field.
• Add concise <<description>> notes to important fields.
• Keep relationship labels tied to actual field names rather than vague business prose.

Minimal example

classDiagram
    class User {
        username: string <<Username>>
        email: email <<Email>>
        display_field() "username"
        required() ["username", "email"]
        unique() ["username", "email"]
    }

    class Order {
        orderNo: string <<Order Number>>
        totalAmount: number <<Total Amount>>
        userId: string <<User ID>>
        display_field() "orderNo"
        unique() ["orderNo"]
    }

    Order "n" --> "1" User : userId

    %% Class naming
    note for User "用户"
    note for Order "订单"

Tool usage guidance

Read existing models

Use this before updating an existing model or when you need naming consistency:

• manageDataModel(action="list")
• manageDataModel(action="get", name="ModelName")
• manageDataModel(action="docs", name="ModelName")

Create or update model

Use modifyDataModel with:

• complete mermaidDiagram
• the correct update mode for create vs update
• a deliberate publish decision

Best practices

1. Prefer direct SQL unless the user clearly benefits from model-first design.
2. Keep the first model iteration small and reviewable.
3. Separate business entities from implementation-only helper fields.
4. Validate relationship direction and ownership before publishing.
5. After modeling, hand off actual SQL/table work to relational-database-tool when needed.