Uml defines thirteen basic diagram types, divided into two general sets:

• Structural
• Behavioral

Events in UML

• Signals: object sent asynchronously by one object and received by another
• Calls: method calls between objects (synchronous)
• Passage of time
• Change in state

Events can also be external or internal

UML Activity Diagrams

Activity diagrams show the workflow of a process from start to finish. Useful for parallel processing.

Components

Step to Construct

1. Find system Actors, Classes and use cases
2. Identify key scenarios of system use cases
3. Combine the scenarios to produce comprehensive workflows described using activity diagrams
4. Where significant object behavior is triggered by a workflow, add object flows to the diagram
5. Where workflows cross technology boundaries, use swim lanes to map the activities
6. Refine complicated high level activities

When to use Activity Diagrams

Use for:

• Analyzing use cases
• understanding workflow across many use cases
• dealing with multi-threaded applications

Do not use for:

• to see how objects collaborate
• to see how an object behaves over its lifetime