Which of the following is a correct statement ?
2016
Which of the following is a correct statement ?
- A.
Composition is a strong type of association between two classes with full ownership.
- B.
Composition is a strong type of association between two classes with partial ownership.
- C.
Composition is a weak type of association between two classes with partial ownership.
- D.
Composition is a weak type of association between two classes with strong ownership.
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Correct answer: A
Key idea: Composition is a strong form of association where the whole has exclusive ownership of its parts; the parts' lifecycles are bound to the whole.
Definition: In composition, one class (the whole) exclusively owns instances of another class (the part). The part cannot meaningfully exist without the whole.
Lifecycle rule: When the whole is destroyed, its composed parts are typically destroyed as well.
UML notation: Composition is shown with a filled (black) diamond at the whole end of the association.
Example: A house composed of rooms — the rooms are considered part of that specific house and are tied to the house's existence in the composition relationship.
Contrast with aggregation: Aggregation is a weaker form of association representing shared or partial ownership; parts can often exist independently of the whole and aggregation is shown with an open (white) diamond.
Conclusion: The correct statement is that composition is a strong type of association with full/exclusive ownership and tied lifecycles.