Activity Diagram
- The main reason to use activity diagrams is to model the workflow behind the system being designed
- Activity diagrams are also useful for analyzing a use case by describing what actions need to take place and when they should occur
- An activity diagram shows the flow from activity to activity
- An activity is an ongoing non-atomic execution within a state machine
Activity diagram contains
- Activity states and action states
- Transitions
- Objects
Action States
- The executable, atomic computations are called action states because; they are states of the system, each representing the execution of an action
- They cannot be decomposed and atomic, meaning that events may occur, but the work of the action state is not interrupted
Activity States
- Activity states can be further decomposed
- Activity states are not atomic, i.e., they may be interrupted
- They take some duration to complete
- Activity states are also special kinds of states in a state machine
Transitions
- Transitions show the path from one action or activity state to the next action or activity state
- A transition is represented as a simple directed line
- Triggerless control passes immediately once the work of the source state is done
Branching
- It represents a branch as a diamond
- A branch, represented as a diamond, may have one incoming transition and two oi more outgoing ones
- Each outgoing transition contains a guard expression, which is evaluated only once on entering the branch
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