Which of the following statements about “total specialization” constraint is…
2017
Which of the following statements about “total specialization” constraint is TRUE?
- A.
Every entity in the subclass must be a member of the superclass.
- B.
Every entity in the superclass must be a member of at least one subclass in the specialization.
- C.
At least one entity in the superclass must be a member of at least one subclass in the specialization.
- D.
Every entity in the superclass must be a member of all subclasses in the specialization.
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Correct answer: B
The Total Specialization constraint (denoted by a double line in ER diagrams) specifies that every entity in the superclass must belong to at least one subclass in the specialization. No superclass entity can exist on its own without being specialized.
Correct Option: B