For any connector, one of its endpoints (the nodes to which it is attached) is its owner (or source). All model information about the connector is stored and versioned as part of the owning model element. By default, the owning end of a connector is indicated in a diagram by a solid semicircle, although you can disable this indicator in the system settings.
For most connectors, ownership is determined by the semantics of the relationship; for example, a conformance link is always owned by the conforming class design. For simple associations, however, ownership is arbitrary, and either endpoint can be the owner. The source element (the element you start with when creating the association) is automatically designated the owner of the association. (This is true for associations created in either the browsers or the diagrammers.) Once you create an association, you cannot change the direction of ownership except by deleting and re-creating it starting with the new source element.
Note: | Direction of ownership is distinct from the UML concept of navigability, which is represented on connector figures by arrowheads. Navigability represents a UML semantic describing whether an association can be traversed in a given direction in the implementation. |