In UML modeling, an extend relationship indicates that
the extension use case extends the behaviors in a base use case.
You must have a least two use cases in a diagram.
To add an extend relationship:
- In the Palette, in the Use Case Diagram drawer,
click Extend.
- Click the extension use case and drag the arrow cursor
to the base use case.
- On the pop-up menu, click Create new Extension
Point.
The extend relationship is added between the base use case
and the extension use case and a new extension point is added to
the Extension Points compartment of the base use case.