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Visual Modeling with Rational Rose 2002 and UML by Terry Quatrani

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Aggregation Relationships

An aggregation relationship is a specialized form of association in which a whole is related to its part(s). Aggregation is known as a “part-of” or containment relationship. The UML notation for an aggregation relationship is an association with a diamond next to the class denoting the aggregate (whole), as shown in Figure 6-3.

Figure 6-3. UML Notation for an Aggregation Relationship

The following tests may be used to determine if an association should be an aggregation:

  • Is the phrase “part of” used to describe the relationship?

  • Are some operations on the whole automatically applied to its parts? For example, delete a course ...

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