johnnystefan/documentation/uml-interaction-diagrams

Skill: Advanced UML — Interaction and Sequence Diagrams

Purpose

This skill enables the agent to document and interpret how objects interact over time using Sequence Diagrams. It is crucial for explaining behavioral patterns like Observer, Mediator, and Command.

Notation Guide

1. Lifelines and Activation

• Lifelines: Vertical dashed lines representing an object's existence over time.
• Activation Bar: Thin rectangle on the lifeline showing when an object is actively performing an operation.

2. Message Arrows

• Synchronous Call: Solid line with a filled arrowhead (waiting for response).
• Return Message: Dashed line with a simple arrowhead.
• Asynchronous Call: Solid line with a simple arrowhead (no waiting).

Procedural Instructions

1. Mapping Patterns to Interaction

• Observer: Show the Publisher sending notify() to all Subscriber lifelines.
• Mediator: Show multiple Component lifelines sending events to the Mediator, and the Mediator dispatching calls back to them.

2. Generating Mermaid Sequence Code

When documenting logic, use the following structure:

sequenceDiagram
  participant A as ClassA
  participant B as ClassB
  A->>B: MethodCall()
  B-->>A: ReturnValue

3. Example: Observer Pattern

sequenceDiagram
  participant S as Store (Publisher)
  participant E as EmailAlert (Subscriber)
  participant L as Logger (Subscriber)
  S->>E: update("stock changed")
  S->>L: update("stock changed")

Payoff

• Clarity in Logic: Visualizes complex message passing that is hard to trace in code.
• Standardized Documentation: Uses industry-standard notation understood by humans and agents.
• Pattern Verification: Confirms that behavioral patterns are implemented correctly.