UML Activity Diagrams

If a use case gets too complex, we use activity diagrams to clarify things

Activity diagrams

are flowcharts

Activity diagrams are UML

Activities are rectangles with rounded corners

Activity-A Activity-B Transition

Transitions are shown by arrows ¡  Sometimes the transition may have text to

explain what is happening

Activity-A Activity-B Transition

Start and Finish ¡ A start is shown by a filled in circle ¡ A finish is a circle containing a filled in circle

Initial Activity End Activity Transition Start Stop

Decisions are denoted by diamonds

Activity-A

Outcome B

Outcome A Decision

Guard conditions block the flow if some condition is not met ¡  They "guard" the door

Synchronization bars ¡ Allow for the branching and joining of

synchronous activities

Activity-A

Activity-B Activity-C

¡  Synchronous means that two or more things are happening simultaneously

Swimlanes show who is responsible for what ¡  Swimlanes are optional

Example

Let's do an example together

Conclusion ¡ When we have a complex use case, UML activity

diagrams can clarify things ¡  They are essentially tightly-defines flowcharts ¡  They use activities, transitions, decisions, guard

conditions, and synchronization bars