You can model the required behavior of a complete system, or portions of a system, with use case diagrams.
Creating use case diagrams
You can create use case diagrams to show the interactions between the use cases and the actors in a system. You can add shapes to use case diagrams to represent the elements of the system, such as use cases and actors, and you can add connectors to show how the shapes interact.Modifying use case diagrams
You can modify use case diagrams to reflect changes in the system that you are modeling.Specifying the relationships in use case diagrams
You can specify relationships to identify the semantic ties that exist between the elements in a model.Adding use case diagrams to models
You can add use case diagrams to models to provide various views of the problem domain. Depending on the complexity of the system you are modeling, you can have multiple diagrams of different types in a single model.
Related concepts
Use case diagrams