Activity Diagram — UML diagram showing workflow or process flow.
When to use:
Components:
Start Node: filled circle (●)
End Node: bullseye (◎)
Activities: rounded rectangles
Decision: diamond (◇)
Fork/Join: thick bars (═══)
Swimlanes: lanes for responsibilities
Example:
[Start] → [Receive Order] → ◇ Stock Available?
Yes → [Process Payment] → [Ship Order]
No → [Notify Customer] → [End]
Benefits: Shows parallel processing, clear workflow.