Activity diagrams are a dynamic UML diagram that can be used to better describe use cases, business flow, software flow or any other type of behavior. Activity diagrams are general purpose in their application.
- Activities can have multiple arrows in but only 1 out (except object flows).
- Activities must have 1 arrow out (never 0).
- Decisions – diamonds – can have multiple arrows in but only 2 out (no more, no less).
- Forks (start of parallelism) can have multiple arrows in and multiple out.
- Join (end of parallelism) can have multiple arrows in and only 1 arrow out.
- Anything that forks must also join at the end.
- It’s OK to have multiple finals on an activity diagram, but you can have (and must have) only 1 start.
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May 15, 2009 at 12:11 am
Please explain why I could not use an activity diagram in place of the Robustness diagram… they appear to express the same information… that it is what interactions take place between the user and the system in a rigorous way… they both seem to be follow the flow of events in the system…
May 15, 2009 at 1:48 am
You could use an activity diagram, but the robustness diagram uses objects from the domain model stereotyped as controllers, boundries, and entities. The activity diagram shows interactions between activities and actions where the robustness shows interactions between objects from the domain model. By adding detail to the robustness diagram, if you keep the domain model in sync with what is added to the robustness diagram, you enrich the domain model, which is the whole purpose of the robustness diagram. Activity diagram is a bit tougher to use to show interaction of actual objects rather than a flow of activities.