Which statement describes aggregation?

Which statement describes aggregation?

• A. The whole destroys its parts when it is destroyed.
• B. Parts can exist independently of the whole.
• C. Parts are always owned and cannot exist without the whole.
• D. The relationship is an is-a relationship.

Answer: (B)

Aggregation is a has-a relationship where the parts can live on independently of the whole. In this kind of association, the lifecycle of the components isn’t tied to the container, and a part can exist without the container or even be related to multiple wholes. That’s why describing parts as able to exist independently of the whole best captures aggregation. By contrast, a statement about the whole destroying its parts when it’s destroyed points to a tighter coupling known as composition, where the parts’ lifetimes are bound to the whole. Saying parts cannot exist without the whole also describes that strong ownership. And calling the relationship is-a refers to inheritance, not aggregation.

Aggregation is a has-a relationship where the parts can live on independently of the whole. In this kind of association, the lifecycle of the components isn’t tied to the container, and a part can exist without the container or even be related to multiple wholes. That’s why describing parts as able to exist independently of the whole best captures aggregation.

By contrast, a statement about the whole destroying its parts when it’s destroyed points to a tighter coupling known as composition, where the parts’ lifetimes are bound to the whole. Saying parts cannot exist without the whole also describes that strong ownership. And calling the relationship is-a refers to inheritance, not aggregation.