ER Modeling Constraints — Covering Requirement for Ternary Relationships Which integrity constraint requires that the associated binary relationship(s) enumerate all combinations that must appear in a related ternary relationship (i.e., the ternary must be covered by the binaries)?

Introduction:
Advanced entity–relationship (ER) modeling includes constraints that relate lower-degree (binary) relationships to higher-degree (ternary) ones. A covering constraint specifies how combinations in binaries correspond to combinations in a ternary association. This question asks you to name the constraint that requires full coverage of the ternary by the binaries.

Given Data / Assumptions:

• We consider a ternary relationship among three entity types (for example, Supplier–Part–Project).
• Binary relationships may exist between each pair (Supplier–Part, Supplier–Project, Part–Project).
• The constraint may require that certain combinations present in binaries appear in the ternary.

Concept / Approach:
The MUST COVER constraint asserts that the specified binary relationships collectively cover all combinations that are required to exist in the ternary relationship. In other words, if a combination is indicated by the binaries under the constraint, it must also be present in the ternary set. This is different from a prohibition constraint (MUST NOT), which forbids certain combinations, and from weaker allowances that do not enforce coverage.

Step-by-Step Solution:
1) Identify that the question seeks a constraint enforcing inclusion (coverage), not exclusion.2) Map “coverage” to the notion that the ternary must contain all combinations implied by binaries.3) Select MUST COVER as the named constraint that encodes this requirement.

Verification / Alternative check:
ER textbooks discussing higher-arity relationships describe covering and exclusion constraints to control permissible tuples in ternary associations. MUST COVER corresponds to required inclusion.

Why Other Options Are Wrong:

• MUST NOT: Expresses exclusion, not required inclusion.
• Both of the above: Mutually inconsistent (coverage vs exclusion).
• None of the above / PARTIAL ALLOW: Do not name the required inclusion constraint.

Common Pitfalls:
Confusing participation constraints (total/partial participation) at the entity level with covering constraints relating binary and ternary relationships.

Final Answer:
MUST COVER