Executable UML: A Foundation for Model-Driven Architecture

6.4. Association Classes

In many cases, we find associations that give rise to additional classes. Usually these additional classes have attributes to capture data that's not properly part of either of the two participating classes. Figure 6.8 shows how to model the association with a third class, an association class, and place the attributes there.

Figure 6.8. The Association Class ProductSelection

Definition: An association class is an abstraction, as a class, of an association that may have its own attributes, other associations, and behavior.

Strictly speaking, an association class is a reification, not an abstraction. An association is already ...