In data modeling, which term refers to an entity whose identifier includes (and depends on) the identifier of another parent entity, such that the child's primary key contains the parent's key?
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AWeak entity
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BStrong entity
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CID-dependent entity
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DID-independent entity
Answer
Correct Answer: ID-dependent entity
Explanation
Introduction / Context:An essential idea in logical data modeling is how one entity's identity can depend on another. When the child's key literally embeds the parent's key, we call that an ID-dependent pattern. This question asks you to name that concept.
Given Data / Assumptions:
- The child entity cannot be uniquely identified without the parent's identifier.
- The child's primary key includes the parent's key (for example, OrderLine has key (OrderID, LineNo)).
- We are reasoning at the logical design level, independent of a specific DBMS.
Concept / Approach:An ID-dependent entity is one whose primary key contains the primary (or candidate) key of its parent entity. This is stronger than merely having a foreign key; here, the foreign key is part of the child's primary key, binding the child's identity to the parent.
Step-by-Step Solution:
Identify the key phrase: “identifier of one entity includes the identifier of another.”Match this to the formal term: ID-dependent entity.Confirm with a classic example: Order (OrderID) and OrderLine (OrderID, LineNo).Verification / Alternative check:Try removing the parent's key from the child's key. If the child would no longer be unique, the entity is ID-dependent.
Why Other Options Are Wrong:
- Weak entity: often used broadly, but the precise term for “identifier includes parent's identifier” is ID-dependent entity.
- Strong entity: its identity is independent.
- ID-independent entity: explicitly the opposite of what is described.
Common Pitfalls:Confusing “has a foreign key” with “is ID-dependent.” Many children have foreign keys; ID-dependence requires the parent's key to be part of the child's primary key.
Final Answer:ID-dependent entity