Which collection type represents an ordered collection of elements (all of the same type) in object data models and OQL? Choose the most appropriate term.
Correct Answer: List
Introduction / Context:Different collection types capture different semantics about order and duplication, which affects query results and method contracts. Knowing these distinctions prevents subtle bugs in persistence and retrieval logic.
Given Data / Assumptions:
- All elements share the same type (typical for declared collections).
- Order matters (positions/indexes are meaningful).
- Standard collection taxonomy applies: set, bag, list, dictionary.
Concept / Approach:
A list is an ordered sequence and typically allows duplicates. A set is unordered and forbids duplicates. A bag is unordered and allows duplicates. A dictionary is keyed by unique keys rather than positional index.
Step-by-Step Solution:
Check the “ordered” requirement → list.Confirm homogeneity (same type) → consistent with list declarations.Answer: List.Verification / Alternative check:
ODMG and many ORMs align “List” with ordered collections; indexes are stable and queries can use positional operations.
Why Other Options Are Wrong:
Set/Bag: explicitly unordered.
Dictionary: key–value store, not a plain ordered sequence.
Common Pitfalls:
Assuming set preserves insertion order; if order is required, do not model as set/bag.
Final Answer:
List