Modeler _modeler_usecase_diagram_system_boundaries
By default, a UseCase diagram does not show its system boundaries. The System Boundaries represent the diagram’s parent package and are used to visually group related elements.
To unmask them, you need to open the Symbol view of the diagram and check the appropriate option:
Keys:
1. Open the Symbol View tray on the diagram’s right-hand side
2. Check the ‘Show System Boundaries’ option
3. The System Boundaries are now visible in the diagram