UML Designer User's Guide

A closer look at associations

Before we add associations to our class diagram, we need to take a close look at associations and their attributes.

The associations we've created up until this point (such as the connection between the Catalog class and the <Catalog> protocol) are more correctly called links. In UML terms, a link is an instance of an association, meaning that a semantic relationship exists between the linked elements. A link represents an instance of one of the types of relationships predefined by the UML and UML Designer metamodels. Protocol conformance is an example of such a relationship; the link between the Catalog class and the <Catalog> protocol is a specific instance of a conformance relationship.

On the other hand, an association defines a type of relationship, but not a specific instance of such a relationship. In other words, an association defines a possible connection between objects in the system defined by your model, rather than being part of the UML or UML Designer metamodel. Another way of looking at it is that an association describes a possible set of links. An association has properties, such as multiplicity, that place constraints on how it can be instantiated.


[ Top of Page | Previous Page | Next Page | Table of Contents | Index ]