# Use Case Diagram

> Creates or updates PlantUML use case diagrams defining actors, use cases, and their relationships from requirements. Use when the user asks to "create a use case diagram", "draw a UML diagram", "map actors to use cases", "generate a .puml file", or mentions PlantUML, use case overview, actor diagram, or system use cases.

- Skill: `nexadevapp/use-case-diagram` (Agent Skill)
- Install (CLI): `npx skillmds@latest add nexadevapp/use-case-diagram`
- Raw SKILL.md: https://api.skillmd.com/api/skills/nexadevapp/use-case-diagram/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: nexadevapp (https://skillmd.com/u/nexadevapp)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/nexadevapp/use-case-diagram

---


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Part of the AI Unified Process — https://unifiedprocess.ai
Licensed under the Apache License, Version 2.0. See LICENSE and NOTICE.

Modifications Copyright 2026 Nexa (nexadev.app).
This file is derived from the AI Unified Process Marketplace and has been
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# Use Case Diagram

## Instructions

Create or update the PlantUML use case diagram at `docs/use_cases.puml` based on `docs/requirements.md`.

## DO NOT

- Create diagrams without reading the requirements first
- Use non-standard PlantUML syntax
- Include implementation details in use case names

## Nexa Rules Gate

Read and follow `${CLAUDE_PLUGIN_ROOT}/shared/readiness/NEXA_RULES_GATE.md`.

## Template

```plantuml
@startuml Use Cases Overview
left to right direction

actor "User" as user
actor "Administrator" as admin

rectangle "System Name" {
    usecase "UC-001\nDescription" as UC001
    usecase "UC-002\nDescription" as UC002
    usecase "UC-003\nDescription" as UC003
}

admin --> UC001
user --> UC002
user --> UC003

@enduml
```

## Conventions

- Each use case has a unique id and a description
- Use Case ID: UC-{3-digit} (UC-001, UC-002, ...)
- **Technical Task ID: TT-{3-digit}** (TT-001, TT-002, ...) — for provisioning, infrastructure,
  or configuration work that a use case depends on but that has no user-facing scenario.
  Technical tasks are represented with a `<<technical>>` stereotype and dashed border.
  Use cases that depend on them use a dotted dependency arrow with a `<<requires>>` label.
  Example:
  ```plantuml
  usecase "TT-010\nProvision OAuth App" as TT010 <<technical>>
  UC045 ..> TT010 : <<requires>>
  ```
- **Use case dependencies** — when a use case cannot be delivered until another use case is
  done, draw the same dotted `<<requires>>` arrow between them:
  ```plantuml
  UC005 ..> UC003 : <<requires>>
  ```
  The diagram is the **visual mirror**. The authoritative declaration is the **Depends On** row
  in `docs/use_cases/UC-XXX.md` — that is what the delivery scheduler parses. Keep the two in
  agreement; when they disagree, the use case specification wins.
- Each use case should trace to at least one functional requirement
- Add notes sparingly, only where relationships need clarification

## Workflow

1. Read the requirements at `docs/requirements.md`
2. Read existing diagram at `docs/use_cases.puml` (if exists)
3. Identify actors and use cases from requirements
4. Create/update the PlantUML use case diagram
5. Validate the diagram:
    - Each use case traces to at least one functional requirement in `docs/requirements.md`
    - All actors are connected to at least one use case
    - Use case IDs follow the UC-{3-digit} convention
    - PlantUML syntax is valid (no missing `@enduml`, proper arrow syntax)