Object relationships in software design — which construct implements a “Has a” relationship?
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APolymorphism
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BTemplates
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CContainership (composition/aggregation)
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DEncapsulation
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EInheritance
Answer
Correct Answer: Containership (composition/aggregation)
Explanation
Introduction / Context:In object-oriented design, relationships between entities are described using specific mechanisms. The “Has a” relationship means one object owns, contains, or aggregates another object.
Given Data / Assumptions:
- We are mapping conceptual relationships to language-agnostic design constructs.
- Terminology: containership includes composition and aggregation.
Concept / Approach:“Has a” corresponds to composition or aggregation (containership). A car “has a” engine; a university “has” departments. The owner object holds references/fields of the component type.
Step-by-Step Solution:
Polymorphism → “is able to behave like many forms” at runtime; not about ownership.Templates (generics) → parameterize types; not a relationship by itself.Containership → models ownership/part-whole → correct.Encapsulation → information hiding; not a relationship type.Inheritance → “Is a/Kind of” relationship, not “Has a”.Verification / Alternative check:Class diagrams: a filled diamond (composition) or hollow diamond (aggregation) from whole to part is the standard notation.
Why Other Options Are Wrong:They describe other OO concepts not matching ownership semantics.
Common Pitfalls:Confusing inheritance (“is a”) with composition (“has a”).
Final Answer:Containership (composition/aggregation)