Session4

Session4 - Session 4: EER: Extended (or Enhanced) ER Model...

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Session 4: EER: Extended (or Enhanced) ER Model (CH-2 and 3) CSCI-585 , Cyrus Shahabi Example ER for a real-world problem Generalization is the result of computing the union of two or more entity sets (or subclasses ) to produce a higher-level entity set (or superclass ). It represents the containment relationship that exists between the higher-level entity set and one or more lower level entity sets. Specialization constructs the lower level entity sets that are a subset of higher-level entity set. Specialization is the reverse of generalization (for the remainder of this session we focus on specialization without loss of generality). Example: (Attribute inheritance) There might exist many specialization of the same entity set based on different distinguishing characteristics. Hence, an entity can be a member of a number of subclasses. Example:
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An entity cannot merely exist by being a member of a subclass but no superclass. However, it is not essential that every entity
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Session4 - Session 4: EER: Extended (or Enhanced) ER Model...

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