The Unified Modeling Language User Guide SECOND EDITION [Electronic resources] نسخه متنی

Chapter 20. Activity Diagrams

In this chapter

• Modeling a workflow

• Modeling an operation

• Forward and reverse engineering

Activity diagrams are one of the five diagrams in the UML for modeling the dynamic aspects of systems. An activity diagram is essentially a flowchart, showing flow of control from activity to activity. Unlike a traditional flowchart, an activity diagram shows concurrency as well as branches of control.

You use activity diagrams to model the dynamic aspects of a system. For the most part, this involves modeling the sequential (and possibly concurrent) steps in a computational process. With an activity diagram, you can also model the flow of values among steps. Activity diagrams may stand alone to visualize, specify, construct, and document the dynamics of a society of objects, or they may be used to model the flow of control of an operation. Whereas interaction diagrams emphasize the flow of control from object to object, activity diagrams emphasize the flow of control from step to step. An activity is an ongoing structured execution of a behavior. The execution of an activity ultimately expands into the execution of individual actions, each of which may change the state of the system or communicate messages.

Activity diagrams are not only important for modeling the dynamic aspects of a system, but also for constructing executable systems through forward and reverse engineering.