Which of the following is NOT a task when refining a conceptual model into a logical model?

Question

BlackTom AI · Accepted Answer

Logical modeling focuses on defining entities, attributes, primary keys, relationships, and normalization while remaining independent of specific DBMS implementation details.

1. Relevant knowledge points and concepts
- Conceptual model: high-level entities, relationships and major attributes; technology-agnostic and informal.
- Logical model: refines the conceptual model into a schema suitable for implementation planning: normalize data, assign primary keys, resolve many-to-many relationships, convert multivalue or composite attributes into proper entities/relationships, and specify foreign-key relationships. It still remains largely DBMS-independent.
- Physical model: maps the logical model to a specific DBMS, choosing concrete data types (e.g., VARCHAR(50), INT), storage parameters and indexes.

2. Step-by-step reasoning
- Start with a conceptual entity-relationship design that may include multivalue attributes and M:N relationships.
- Convert any multivalue attribute into a separate entity or relationship (e.g., an attribute “phone numbers” becomes a Phone entity linked to Person).
- Resolve many-to-many relationships by introducing an associative entity (junction table) that holds the two primary keys and any relationship attributes.
- Add foreign keys in the logical model to express referential integrity between the newly created relations and their parent entities.
- Choosing concrete database-specific data types (VARCHAR, DECIMAL, etc.) is deferred to the physical model.

3. Calculations
- No numeric calculations are needed.

4. Why the correct answer is correct
- "Define data types for all attributes" is primarily a physical modeling task. While the logical model may define domains or general types conceptually (e.g., “integer”, “string”), assigning specific DBMS data types and sizes belongs to the physical design stage, so it is NOT a task when refining conceptual into logical.

5. Why the other options are incorrect
- Resolve many-to-many entity relationships: This is a core logical-model task (create associative entity).
- Add foreign keys: Logical models define foreign-key relationships to maintain referential integrity.
- Convert multivalue attributes: Logical modeling converts multivalue attributes into separate entities or relationships.

6. Conclusion
Therefore, the correct answer is "Define data types for all attributes," which matches the provided answer.

Which of the following is NOT a task when refining a conceptual model into a logical model?单项选择题

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