In object-oriented design, which statement best describes composition?

In object-oriented design, which statement best describes composition?

• A. The whole can exist without its parts.
• B. Parts survive independently of the whole.
• C. The relationship is based on is-a.
• D. A part belongs to the whole and is destroyed with it.

Answer: (D)

Composition captures the idea of strong ownership: a whole controls the creation and lifecycle of its parts. The statement that a part belongs to the whole and is destroyed with it expresses that lifecycle tie—when the whole is created, the parts are created as part of it, and when the whole is destroyed, the parts are released as well. This makes the parts non-sharable and not expected to survive independently of the container. It contrasts with the idea of parts existing independently or with an is-a relationship, which describe different concepts entirely: independent parts point to aggregation or ordinary associations, while is-a refers to inheritance rather than containment. So the described property—exclusive ownership and tied lifecycles—best captures composition.

Composition captures the idea of strong ownership: a whole controls the creation and lifecycle of its parts. The statement that a part belongs to the whole and is destroyed with it expresses that lifecycle tie—when the whole is created, the parts are created as part of it, and when the whole is destroyed, the parts are released as well. This makes the parts non-sharable and not expected to survive independently of the container. It contrasts with the idea of parts existing independently or with an is-a relationship, which describe different concepts entirely: independent parts point to aggregation or ordinary associations, while is-a refers to inheritance rather than containment. So the described property—exclusive ownership and tied lifecycles—best captures composition.