Question at position 38 Supertype/subtype relationships should not be used when instances of a subtype do not participate in any relationships unique to that subtype and have no unique attributes.TrueFalse单项选择题
A
True
B
False

Question

Question at position 38 Supertype/subtype relationships should not be used when instances of a subtype do not participate in any relationships unique to that subtype and have no unique attributes.TrueFalse单项选择题

A

True

B

False

BlackTom AI · Accepted Answer

Supertype/subtype relationships capture specialization: when an entity set (supertype) has subsets (subtypes) that possess attributes or participate in relationships not shared by the supertype.

1. Relevant knowledge points and concepts
- Supertype/subtype (specialization) in ER modeling is justified when subtypes have unique attributes or participate in relationships exclusive to them.
- If no unique attributes or relationships exist, specialization introduces redundancy and unnecessary complexity; a single entity type with a discriminating attribute (or none) suffices.
- Design goals: clarity, normalization, minimal redundancy, and maintainability.

2. Step-by-step reasoning
- Step 1: Identify whether subtype adds new information (attributes) or associations (relationships) that are not part of the supertype.
- Step 2: If neither exists, the subtype does not represent additional data or constraints; it is only a semantic label.
- Step 3: Creating separate subtype structures would require extra schema elements (tables, keys, integrity rules) without modeling benefit.
- Step 4: Better alternative: keep a single entity (the supertype) and, if needed, add a simple discriminator attribute or document the semantic role.

3. Intermediate considerations
- No numerical calculations apply; reasoning is conceptual. Intermediate check: unique attribute? No. Unique relationship? No. Therefore specialization is not justified.

4. Why the correct answer is correct
- The statement asserts that supertype/subtype should not be used in the absence of unique subtype attributes or relationships. This aligns with modeling best practices: avoid unnecessary specialization that increases schema complexity and redundancy.

5. Why the other option is incorrect
- Choosing False would imply that you should use subtypes even when they add no unique attributes or relationships; that contradicts normalization and good design principles and leads to needless complexity.

6. Conclusion
- The correct answer is True, which matches the provided answer.

Question at position 38 Supertype/subtype relationships should not be used when instances of a subtype do not participate in any relationships unique to that subtype and have no unique attributes.TrueFalse单项选择题

类似问题

Generalization is a process that proceeds:

A derived attribute is one that:

An example of total and disjoint specialization would be:

Which of the following is TRUE about a Total Disjoint Constraint in specialization?

Question at position 47 The number of entity types that participate in a relationship is called the: degree.counter.number.identifying characteristic.

Question at position 48 The subtype discriminator is a composite attribute when there is a(n):disjoint rule.partial specialization.overlap rule.full specialization.

Question at position 39 The name used for an entity type should never be the same in other E-R diagrams on which the entity appears. TrueFalse

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单