In this chapter
Use case diagrams are one of the diagrams in the UML for modeling the dynamic aspects of systems. (Activity diagrams, state diagrams, sequence diagrams, and communication diagrams are four other kinds of diagrams in the UML for modeling the dynamic aspects of systems.) Use case diagrams are central to modeling the behavior of a system, a subsystem, or a class. Each one shows a set of use cases and actors and their relationships.
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Activity diagrams are discussed in Chapter 20; state diagrams are discussed in Chapter 25; sequence and communication diagrams are discussed in Chapter 19 . |
You apply use case diagrams to model the use case view of a system. For the most part, this involves modeling the context of a system, subsystem, or class, or modeling the requirements of the behavior of these elements.
Use case diagrams are important for visualizing, specifying, and documenting the behavior of an element. They make systems, subsystems, and classes approachable and understandable by presenting an outside view of how those elements may be used in context. Use case diagrams are also important for testing executable systems through forward engineering and for comprehending executable systems through reverse engineering.