In data modeling, which situations typically require using ID-dependent (identifying) entities whose primary keys include the parent’s key?

Difficulty: Medium

Correct Answer: All of the above use ID dependent entities

Explanation:


Introduction / Context:
ID-dependent (identifying) entities are entities whose primary key includes the primary key of a parent entity. This modeling pattern expresses strong ownership and ensures a child cannot exist without its parent. It is useful in several recurring scenarios in logical design.



Given Data / Assumptions:

  • An identifying relationship implies the child’s PK includes the parent’s PK.
  • We consider association entities, multivalued attributes, and archetype/instance structures.
  • The target is a relational schema derived from an ER/EER model.


Concept / Approach:
Association (intersection) entities in many-to-many relationships often use a composite PK built from the parent PKs, making them ID-dependent on both parents. Multivalued attributes become separate child entities keyed by the parent's key plus a discriminator, thus ID-dependent. Archetype/instance patterns may use an identifying relationship to tie instances to their archetype via a composite identifier.



Step-by-Step Solution:

Identify ownership: the child makes no sense without the parent (for example, OrderLine depends on Order).Model the child’s PK to include the parent’s PK, forming an identifying (solid-diamond) relationship.For M:N associations, create an associative entity whose PK includes both parents’ PKs.


Verification / Alternative check:
Attempt to define the child without the parent key; if uniqueness breaks or orphan rows become possible, ID-dependence is indicated.



Why Other Options Are Wrong:

  • Options a/b/c each name a valid use, but not exclusively. The pattern applies to all of them.
  • None of the above: Incorrect, as the scenarios listed are classic uses.


Common Pitfalls:
Overusing surrogate keys and losing the identifying tie. Even with a surrogate, keep a UNIQUE constraint on the natural identifying columns to preserve semantics.



Final Answer:
All of the above use ID dependent entities

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