Change Aggregation Connector Form
In your modeling, when you create an Aggregation relationship it defaults to the weak (shared) form of the relationship, represented by a hollow diamond head. You can change this to the strong form (Composition), represented by a solid black diamond head.
Change the form of an Aggregation connector from weak to strong
Right-click on an Aggregation connector to display the context menu.
Select Set Aggregation to Composite.
The diamond is shown as filled.
- If the connector is already a Strong (Composition) connector, the context menu option changes to 'Set Aggregation to Shared'