Use of Extended E-R Features
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.