| Concept Of Enhanced ER Diagram |
We have seen weak entity sets, generalization and aggregation. Designers must
decide when these features are appropriate.
- Strong entity sets and their dependent weak entity sets may be regarded
as a single ``object'' in the database, as weak entities are
existence-dependent on a strong entity.
- It is possible to treat an aggregated entity set as a single unit
without concern for its inner structure details.
- Generalization contributes to modularity by allowing common attributes
of similar entity sets to be represented in one place in an E-R diagram.
Excessive use of the features can introduce unnecessary complexity into the
design.
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