Shared aggregation | Glossary

Definition:

Shared aggregation (aggregation) is a binary association between a property and one or more composite objects which group together a set of instances. It is a “weak” form of aggregation when part instance is independent of the composite. Shared aggregation has the following characteristics:

  • it is binary association,
  • it is asymmetric – only one end of association can be an aggregation,
  • it is transitive – aggregation links should form a directed, acyclic graph, so that no composite instance could be indirect part of itself,
  • shared part could be included in several composites, and if some or all of the composites are deleted, shared part may still exist.

Further Reading:

Book: The Unified Modeling Language Reference Manual by James Rumbaugh, Ivar Jacobson and Grady Booch.

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