Visual Modeling with Rational Rose 2002 and UML

The Need for Relationships

All systems are made up of many classes and objects. System behavior is achieved through the collaborations of the objects in the system. For example, a student is added to a course offering when the course offering receives the add student message. This is often referred to as an object sending a message to another object. Relationships provide the conduit for object interaction. Two types of relationships discovered during analysis are associations and aggregations.