Activity Diagrams

An activity usually represents a set of actions where execution may cause a change in the state of the system or return a result. An action is a step within the activity. An activity diagram is much like a flowchart that shows the flow of control from activity to activity [BRJ99]. Activity diagrams are one of the UML diagrams that are used to model dynamic aspects of systems. Usually they are used to model sequential execution of steps that starts with an initial state and ends with an end state. Activity diagrams can be used to model concurrent execution of steps in a workflow.

An example of an activity diagram is shown in Figure 6-10. An activity is an ongoing nonatomic execution within a state machine [BRJ99]. An activity diagram always starts with a start state (or initial state) represented by a filled bullet. Arrows show the transition from one activity to the next one. As an example, in Figure 6-10, when the execution of activity initialize weather is terminated, then the execution of the next activity named initialize soil takes place.

[plant not matured]

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