When you model advanced relationships in the UML, remember that there is a wide range of building blocks at your disposal, from simple associations to more-detailed properties of navigation, qualification, aggregation, and so on. You must choose the relationship and the details of that relationship to best fit your abstraction. A well-structured relationship
Exposes only those features necessary for clients to use the relationship and hides all others.
Is unambiguous in its intent and semantics.
Is not so overly specified that it eliminates all degrees of freedom by its implementers.
Is not so underspecified that it renders the meaning of the relationship ambiguous.
When you draw a relationship in the UML,
Show only those properties of the relationship that are important to understanding the abstraction in its context.
Choose a stereotyped version that provides the best visual cue to the intent of the relationship.