Chapter 12 – Modeling Functionality with Use Cases

Publisher Summary This chapter describes how to model the high-level functionality of a system with use cases. Use cases describe the functionality of a system in terms of how it is used to achieve the goals of its various users. The users of a system are described by actors, which may represent external systems or humans who interact with the system. Actors can be classified using generalization. Use cases can also be classified using generalization, but in addition one use case may include or extend other use cases. Actors must be related to the use cases in which they are participants. The relationships between the system under consideration, its actors, and use cases are described on a use case diagram. Use cases have been viewed as a mechanism to capture system requirements in terms of the uses of the system. SysML requirements can be used to more explicitly capture text requirements with relationships to use cases and other model elements. The steps in a use case description can also be captured as SysML requirements.