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# Association ,Composition, Aggregation

sarma kiran
Ranch Hand
Posts: 30
Can any one tell me the differece between composition, association and aggregation with some example.

Ulf Dittmer
Rancher
Posts: 42968
73
Start here: AssociationVsAggregationVsComposition

Don Solomon
Ranch Hand
Posts: 48
Both Composition and Aggregation are Associations.
Composition IS-A Association.
Aggregation IS-A Association.

Composition is a strong association.
Aggregation is a weak association.

Composition indicates that the lifetime of an object is dependent on another object. Not so with Aggregation.

When the house is "destroyed", its composites (int-squarefeet, Floor-material) are also "destroyed". These are strong associations. The DriveWay still remains; this is a weak association.

Nandakumar Rajamanickam
Greenhorn
Posts: 5
Composition IS-A Association.
Aggregation IS-A Association.

it should be HAS-A instead of IS-A

Ranch Hand
Posts: 449
sarma kiran wrote:Can any one tell me the differece between composition, association and aggregation with some example.

Both aggregation and composition are special kinds of associations. Aggregation is used to represent ownership or a whole/part relationship, and composition is used to represent an even stronger form of ownership. With composition, we get coincident lifetime of part with the whole. The composite object has sole responsibility for the disposition of its parts in terms of creation and destruction.

Moreover, the multiplicity of the aggregate end may not exceed one; i.e., it is unshared. An object may be part of only one composite at a time. If the composite is destroyed, it must either destroy all its parts or else give responsibility for them to some other object. A composite object can be designed with the knowledge that no other object will destroy its parts.

see compostion and aggregation