Entity clustering definition: Is an entity cluster a set of one or more entity types along with their associated relationships, grouped to simplify an ERD view?
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ACorrect
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BIncorrect
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CCorrect only for physical diagrams
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DCorrect only when subtypes are present
Answer
Correct Answer: Correct
Explanation
Introduction / Context:Large ERDs quickly become difficult to read. To improve comprehension, modelers use “entity clusters,” which aggregate related entities and their relationships into a single visual unit on a diagram. This question checks the correct definition of an entity cluster.
Given Data / Assumptions:
- An ERD view contains many entities and relationships.
- We want a diagramming abstraction that hides detail while preserving conceptual connections.
- Clustering is about presentation on a view, not about altering the underlying logical model.
Concept / Approach:An entity cluster is precisely a set of one or more entity types and their relationships grouped for readability. It does not change keys, cardinalities, or normalization; it merely replaces a group of boxes and lines with a single cluster icon on that view. Analysts can drill into the cluster to see the underlying detailed entities when needed.
Step-by-Step Solution:
Identify a cohesive group of entities (for example, Payment, Payment_Method, Currency).Create a cluster in the modeling tool and move those entities and relationships into it.Expose cluster-level connections to the rest of the model to maintain diagram flow.Use multiple views: high-level for stakeholders, detailed for developers and DBAs.Verification / Alternative check:Compare the diagram before and after clustering; the number of shapes is reduced, but the underlying repository still lists all original entities and relationships unchanged.
Why Other Options Are Wrong:
- “Incorrect” misrepresents the textbook definition.
- Tying clustering to physical diagrams or to subtyping is unnecessary; it is a general diagramming technique applicable to many scenarios.
Common Pitfalls:Misusing clusters as a replacement for proper normalization, or hiding critical relationships that stakeholders need to review. Ensure clusters are used to enhance, not obscure, understanding.
Final Answer:Correct