UML Use Case Relationships

This section describes how to relate use cases to each other. A dashed line between use cases is used to indicate these relationships.

• Include - Subroutine - Factors out and organizes common subtasks. Extra behavior is added into a base use case. This behavior describes the insertion explicitly. The included use case is not a complete process. Use "include" when multiple use cases have a common function that can be used by all. Dashed line with arrow points to subroutine use case.
• Extend - Rarely used - Must perform a pre-task (Used only for critical order). The base and extended use cases are complete processes on their own. The base use case does not know about the extended use case. Arrow points to event that comes first.
• Generalization-specialization (Gen-Spec) - The gen-spec use case adds features to a generic use case. The gen-spec use case inherits features of the base use case. The gen spec can be used for use cases and actors since both can be specialized.