Question

Use of a supertype/subtype relationship is necessary when which of the following exists?

(a) An instance of a subtype participates in a relationship that is unique to that subtype

(b) An instance of a subtype participates in a relationship that is the same as the other subtypes

(c) Attributes apply to all of the instances of an entity type

(d) No attributes apply to any of the instances of an entity type

I got this question in my homework.

My doubt is from The Atomic Data Models and Business Models topic in division Planning Oracle Applications of Oracle

Answer 1

Right answer is (a) An instance of a subtype participates in a relationship that is unique to that subtype

The explanation: Super-types and sub-types show hierarchy in the structure; graphs and trees show hierarchy in the data.