Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Specialization and Generalization

  • Bernhard ThalheimEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_175


Abstraction; Hierarchies; Refinement


Specialization and generalization are main principles of database modeling. Specialization is based on a refinement of types or classes to more specific ones. Generalization maps or groups types or classes to more abstract or combined ones. Typically, generalizations and specializations form a hierarchy of types and classes.

Key Points

Specialization introduces a new entity type by adding specific properties belonging to that type, which are different from the general properties of its more general type. Is-A associations specialize a type to a more specific one. Is-A-Role-Of associations consider a specific behavior of objects. Is-More-Specific-To associations specialize properties of objects of the more general type. The student type and the customer type are specializations of the person type. The rectangle type is specialized to the squaretype by adding restrictions. Different kinds of specialization may be distinguished:...

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Recommended Reading

  1. 1.
    Ter Bekke JH. Semantic Data Modeling. London: Prentice-Hall; 1992.Google Scholar
  2. 2.
    Thalheim B. Entity-Relationship Modeling - Foundations of Database Technology. Berlin/Hiedelberg/New York: Springer; 2000.zbMATHCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Christian-Albrechts UniversityKielGermany

Section editors and affiliations

  • David W. Embley
    • 1
  1. 1.Brigham Young UniversityProvoUSA