GATE CS 2024 Set 2 | Question 20

MCQ · 1 mark · −0.33

In the context of owner and weak entity sets in the ER (Entity-Relationship) data model, which one of the following statements is TRUE?

  1. Option A: The weak entity set MUST have total participation in the identifying relationship (correct)
  2. Option B: The owner entity set MUST have total participation in the identifying relationship
  3. Option C: Both weak and owner entity sets MUST have total participation in the identifying relationship
  4. Option D: Neither weak entity set nor owner entity set MUST have total participation in the identifying relationship

Answer

(A)

Explanation

A weak entity set has no key of its own. A weak entity is identified only by combining its partial key (discriminator) with the key of the owner entity it is linked to through the identifying relationship. A weak entity without an owner could not be identified at all, so every weak entity must take part in that relationship: the weak entity set has total participation.

The owner side has no such requirement. With Employee as the owner and Dependent as the weak entity set, for example, an employee may have no dependents. So the owner's participation can be partial, which rules out B and C, and D fails because the weak side must be total.

Answer: A