Include relationships

In UML modeling, an include relationship is a relationship in which one use case (the base use case) includes the functionality of another use case (the inclusion use case). The include relationship supports the reuse of functionality in a use-case model.

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

The behavior of the inclusion use case is common to two or more use cases.
The result of the behavior that the inclusion use case specifies, not the behavior itself, is important to the base use case.

Include relationships usually do not have names. If you name an include relationship, the name is displayed beside the include connector in the diagram.

As the following figure illustrates, an include relationship is displayed in the diagram editor as a dashed line with an open arrow pointing from the base use case to the inclusion use case. The keyword «include» is attached to the connector.

Two ovals connected by a dashed line with an open arrow

Example

The following figure illustrates an e-commerce application that provides customers with the option of checking the status of their orders. This behavior is modeled with a base use case called CheckOrderStatus that has an inclusion use case called LogIn. The LogIn use case is a separate inclusion use case because it contains behaviors that several other use cases in the system use. An include relationship points from the CheckOrderStatus use case to the LogIn use case to indicate that the CheckOrderStatus use case always includes the behaviors in the LogIn use case.

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