A use case diagram shows a visual representation of your use cases and actors and the relationships among them. In addition, a use case diagram shows the system boundary (represented in UML Designer by a Group element).
The following tools are available in the Use Case Diagrammer:
![]() | Selection: Allows selection and manipulation of existing figures. |
![]() | Pan/zoom: Controls the size and position of the viewing area. |
![]() | System: Creates a System figure, representing the grouping of elements that make up the system. |
![]() | Use case: Creates a use case figure. |
![]() | Actor: Creates an actor figure. |
![]() | Annotation: Creates a figure representing a note, comment, or constraint. |
![]() | Association: Creates a "uses" link between use cases. |
![]() | Extension: Creates an "extends" link between use cases. |
![]() | Constraint annotation: Creates a link between a constraint annotation and a design element. |
![]() | Sticky: Allows creation of multiple figures without reselecting on the tool bar. |
Each system figure in a use case diagram represents a system or subsystem and is attached to a Group model element. You cannot attach a system figure to a group that already contains use cases.
Placing a use case figure within a system figure also adds the use case element to the corresponding group. If you move the use case figure outside the system figure, the use case element is removed from the group. A use case figure outside a system figure has a dotted border; a use case inside a system figure has a solid border.
Select Hide/Show Relationships from the pop-up menu of a use case figure to select from a list of existing and candidate relationships to other model elements. Candidate relationships between use cases and actors, indicated by a plus sign (+), are chosen based on the hypertext links that occur in the text of the use case. If you select a candidate relationship, UML Designer prompts you to confirm the direction of the relationship before creating it.