Databases Illuminated, 4th Edition

3.10 Generalization and Specialization

The process of generalization and its inverse, specialization, are two abstractions that are used to incorporate more meaning in EER diagrams.

3.10.1 Specialization

Often an entity set contains one or more subsets that have special attributes or that participate in relationships that other members of the same entity set do not have. For instance, in the University example whose ER diagram is shown in Figure 3.13, the Faculty entity set can be broken up into subsets, AdjunctFac and FullTimeFac. Adjunct faculty members teach part-time and are usually appointed on a temporary basis, while full-time faculty are regular employees who work on a continuing basis. Adjunct faculty members are paid per course, while ...