In ERD notation, what term specifies the minimum number of entity instances that must participate in a relationship?
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AMinimum cardinality
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BMaximum cardinality
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CERD
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DGreater Entity Count (GEC)
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EParticipation degree
Answer
Correct Answer: Minimum cardinality
Explanation
Introduction / Context:Cardinality constraints include both an upper bound and a lower bound. The lower bound indicates whether participation is optional (0) or mandatory (1 or more). Correctly capturing this avoids orphaned or incomplete data.
Given Data / Assumptions:
- We want the minimum number of related instances required.
- ER models reflect this as optionality or mandatory participation.
- Common notations: 0..1, 1..1, 0.., 1...
Concept / Approach:Minimum cardinality is the lower bound of a relationship. A value of 0 means optional involvement; 1 means mandatory. This propagates to referential constraints and application validations in implementation.
Step-by-Step Solution:
Identify lower versus upper bound → minimum cardinality is lower bound.Map to optional/mandatory rules for business logic and database constraints.Ensure DDL and application enforce the intended minimum cardinalities.Verification / Alternative check:ER references consistently define lower bound as minimum cardinality.
Why Other Options Are Wrong:Maximum cardinality: Upper bound, not lower. ERD / GEC / Participation degree: Not the specific term for the minimum bound in standard ER vocabulary.
Common Pitfalls:Failing to align optionality in ERD with NOT NULL and foreign key constraints at implementation time.
Final Answer:Minimum cardinality