Aggregation Association icon Aggregation Association Relationships
   

An aggregation association is a relationship that indicates that one classifier is a part of or subordinate to another classifier. Data flows from the whole classifier to the part. A part classifier may belong to more than one aggregate classifier, and it may exist independently of the aggregate. Aggregation is closely related to composition.

An example of a Unified Modeling Language Aggregation Association showing the relationship between a vehicle and one of its doors