Use case diagrams

Use case diagrams model the behavior of a system and help to capture the requirements of the system.

Use case diagrams describe the high-level functions and scope of a system. These diagrams also identify the interactions between the system and its actors. The use cases and actors in use case diagrams describe what the system does and how it is used by the actors, but not how the system operates internally.

Use case diagrams illustrate and define the context and requirements of either an entire system or the important parts of the system. You can model a complex system with a single use case diagram, or create many use case diagrams to model the components of the system. You would typically develop use case diagrams in the early phases of a project and refer to them throughout the development process.

Use case diagrams are helpful in the following situations:

The following topics describe model elements in use case diagrams:

Related tasks
Modeling the behavior of a system by using use case diagrams
Creating use case diagrams
Adding use case diagrams to models
Modifying use case diagrams
Specifying the relationships in use case diagrams

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