Chapter 4


Chapter 4

Enhanced Entity-Relationship and UML

Modeling

3Elmasri and Navathe, Fundamentals of Database Systems, Fourth Edition


FIGURE 4.1EER diagram notation to represent subclasses and specialization.



FIGURE 4.2Instances of a specialization.



FIGURE 4.3Generalization. (a) Two entity types, CAR and TRUCK. (b) Generalizing CAR and TRUCK into the superclass VEHICLE.



FIGURE 4.4EER diagram notation for an attribute-defined specialization on JobType.



FIGURE 4.5EER diagram notation for an overlapping (nondisjoint) specialization.



FIGURE 4.6A specialization lattice with shared subclass ENGINEERING_MANAGER.



FIGURE 4.7A specialization lattice with multiple inheritance for a UNIVERSITY database.



FIGURE 4.8Two categories (union types): OWNER and REGISTERED_VEHICLE.



FIGURE 4.9An EER conceptual schema for a UNIVERSITY database.



FIGURE 4.10A UML class diagram corresponding to the EER diagram in Figure 4.7, illustrating UML notation for specialization/generalization.



FIGURE 4.11Ternary relationship types. (a) The SUPPLY relationship. (b) Three binary relationships not equivalent to SUPPLY. (c) SUPPLY represented as a weak entity type.



FIGURE 4.12Another example of ternary versus binary relationship types.



FIGURE 4.13A weak entity type INTERVIEW with a ternary identifying relationship type.



FIGURE 4.14a,bAggregation. (a) The relationship type INTERVIEW. (b) Including JOB_OFFER in a ternary relationship type (incorrect).



FIGURE 4.14cAggregation. (c) Having the RESULTS_IN relationship participate in other relationships (generally not allowed in ER).



FIGURE 4.14dAggregation. (d) Using aggregation and a composite (molecular) object (generally not allowed in ER).



FIGURE 4.14eAggregation. (e) Correct representation in ER.



FIGURE 4.15EER schema for a SMALL AIRPORT database.

Chapter 4

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