Definition: An association is the abstraction of a set of domain relationships that hold systematically between different kinds of conceptual entities, abstracted as classes, in the domain.
Author WRITES Book
Publisher PRODUCES AND MARKETS Book
Customer PURCHASES Book
The association is stated in terms of the classes abstracted from the domain.
Associations are shown on the class diagram as lines drawn between the two participating classes. The lines on the diagram are labeled with the association names, association ends, and multiplicities.
Each association has a name. The name is an arbitrary identifier that can be meaningful to the association or can simply be a label, such as R12 for the “twelfth relationship.” ...