Executable UML: A Foundation for Model-Driven Architecture

Classes don't exist in isolation; they are interrelated. To formalize our knowledge of a domain, we must identify how the conceptual entities in the domain are associated and reflect these associations as precisely stated relationships in the model.

A UML relationship covers associations, generalization, and dependencies. Executable UML defines associations between classes, association classes that formalize associations, and generalization. We do not cover dependencies in this chapter.

We use the term domain relationship to describe relationships between things abstracted as classes in the domain under study.