What is aggregation?
Created May 4, 2012
John Moore Aggregation is a special kind of association
that specifies a whole/part relationship between
the aggregate (whole) and a component part.
When compared to an ordinary association, some
distinguishing characteristics of
aggregation include:
- aggregation is an asymmetric relationship
- aggregation is a transitive relationship
- aggregation implies stronger coupling
- behavior (copy, delete, etc.) is normally propagated across an aggregation.
The decision to use aggregation is largely a matter of judgement. James Rumbaugh suggests that, when in doubt, use an ordinary association.