Activity Diagram |
Activity diagrams are a variation of state diagrams which show the sequence of activity states (states that are doing something). The diagram can show conditional and parallel behaviour.
The initial state is the starting state with reference to the behaviour that the diagram explains. Each activity diagram should have only one initial state. A final state represents one of the possible ending states.
A fork is a way of showing that a single incoming transition triggers several outgoing transitions. These activities occur in parallel. Since all of the activities must occur synchronously, you must have a join that joins together the flows of execution started by each fork.
A branch is a way of showing how a single incoming transition may take one of several outgoing transitions. Each outgoing transition must have a guard that makes it mutually exclusive to the others.