Specialization rule: If an entity instance may belong to multiple subtypes or may belong to no subtype at all, how is the supertype/subtype design characterized?
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ADisjoint with total specialization
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BDisjoint with partial specialization
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COverlap with total specialization
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DOverlap with partial specialization
Answer
Correct Answer: Overlap with partial specialization
Explanation
Introduction / Context:Two key decisions in supertype/subtype modeling are disjointness (disjoint vs. overlap) and completeness (total vs. partial). These affect constraints and implementation.
Given Data / Assumptions:
- The same supertype instance can appear in more than one subtype → overlap.
- An instance might be in no subtype → partial specialization.
Concept / Approach:Overlap means an instance may exist in multiple subtypes simultaneously. Partial means membership in at least one subtype is not required. Together, they describe “overlap with partial specialization.”
Step-by-Step Solution:
Interpret “multiple subtypes” → overlap.Interpret “does not have to be a member” → partial.Combine into the correct pairing.Verification / Alternative check:Modeling notations (crow’s foot, UML generalization sets) support these exact options.
Why Other Options Are Wrong:Disjoint: Conflicts with multiple membership. Total: Requires membership in at least one subtype, which the stem denies.
Common Pitfalls:Confusing total/partial with disjoint/overlap; they are independent choices.
Final Answer:Overlap with partial specialization