Generalization is a process that proceeds:

Question

BlackTom AI · Accepted Answer

Generalization is the process of creating a broader, more abstract supertype by combining common features of several specialized subtypes, so it proceeds bottom-up from specialized to generalized entities.

Relevant knowledge points:
- In Entity-Relationship modeling, specialization and generalization are inverse operations. Specialization is top-down (supertype → subtypes); generalization is bottom-up (subtypes → supertype).
- A supertype represents common attributes/relationships shared by multiple subtypes; subtypes represent specialized entities with additional attributes or constraints.
- Generalization is used to reduce redundancy and capture shared semantics.

Step-by-step reasoning:
1. Identify specialized entities (subtypes) that have overlapping attributes or similar relationships. Example: Employee and Student both have Name, DateOfBirth.
2. List common attributes and relationships among these subtypes.
3. Create a new supertype (e.g., Person) that holds the common attributes.
4. Define ISA relationships linking each subtype to the supertype, and move the common attributes up to the supertype while keeping subtype-specific attributes with each subtype.
5. Verify integrity constraints (disjoint/overlap, total/partial participation) to ensure model correctness.

Why the correct answer is correct:
- The defining characteristic of generalization is aggregation of specificity into generality; you begin with specific, specialized entities and synthesize them into a generalized entity. This is precisely bottom-up from specialized to generalized entities.

Why the other options are incorrect:
- “From simple attributes to composite attributes”: refers to attribute modeling, not generalization/specialization of entities.
- “From weak entities to strong entities”: concerns identifying entity types with/without primary keys and identifying relationships; not the generalization process.
- “Top-down from a supertype to each of the subtypes”: describes specialization (creating subtypes), the opposite of generalization.

Conclusion: Therefore, generalization proceeds bottom-up from specialized to generalized entities, matching the provided correct answer.

Generalization is a process that proceeds:单项选择题

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