The functional requirements of a system under development (i.e., the functionality that must be provided by the system) are documented in a use case model that illustrates the system’s intended functions (use cases), its surroundings (actors), and relationships between the use cases and actors (use case diagrams). At the same time, it is useful to see the flow of control and the flow of data between the different scenarios represented in a use case. Activity diagrams are used to visually document the different flows in a use case.
The most important role of a use case model is one of communication. It provides ...