A directed association indicates that control flows from one classifier to another; for example an actor to a use case. This flow of control means that only one of the association ends specifies navigability.
If you use association end names, you do not typically need to name an association. You can, however, name any association to describe the nature of the relationship between the two classifiers.
A directed association is displayed as a solid line with an arrow that
indicates the direction of navigation.