Include Relationships

An include relationship specifies that a base use case uses the behavior defined in another use case (inclusion use case). The inclusion relationship signifies that the incorporation of the inclusion use case is unconditional, meaning the inclusion use case is always executed when the spot in the base use case where it is inserted is reached. The inclusion use case is abstract.

For example, an e-commerce application may provide customers with the option of checking the status of their orders. One way to model this behavior is with a base use case called "Check Order Status" that has an inclusion use case called "Log In." The "Log In" use case is a separate inclusion use case because it contains behaviors that are used by a number of other use cases in the system. In the use-case diagram, an include relationship points from the "Check Order Status" use case to the "Log In" use case to indicate that the behaviors in the "Log In" use case are always included in the "Check Order Status" use case.

An include relationship appears as a dashed line with an arrow pointing from the base use case to the inclusion use case. The keyword «include» is attached to the connector.

You can add include relationships to your model to show the following:

• The behavior of the inclusion use case is common to two or more use cases.

• The result of the behavior specified in the inclusion use case, not the behavior itself, is important in the base use case.

The extend relationships in a model usually appear in use-case diagrams.

• Adding and Modifying Relationships
• Working with Use-Case Diagrams

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