Encyclopedia of Database Systems

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

Object Identity

  • Susan D. UrbanEmail author
  • Suzanne W. Dietrich
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1470


Object identifier; Object reference; OID


Object identity is a property of data that is created in the context of an object data model, where an object is assigned a unique internal object identifier, or OID. The object identifier is used to define associations between objects and to support retrieval and comparison of object-oriented data based on the internal identifier rather than the attribute values of an object.

Key Points

In an object data model, an object is created as an instance of a class. An object has an object identifier as well as a state. An object identifier is immutable, meaning that the value of the object identifier cannot change over the lifetime of the object. The state, on the other hand, is mutable, representing the attributes that describe the object and the relationships that define associations among objects. Relationships in an object data model are defined using object references based on internal object identifiers rather than attribute...

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Recommended Reading

  1. 1.
    Beeri C, Thalheim B. Identification as a primitive of database models. In: Proceedings of the 7th International Workshop on Foundations of Models and Languages for Data and Objects; 1998. p. 19–36.CrossRefGoogle Scholar
  2. 2.
    Koshafian S, Copeland G. Object identity. ACM SIGPLAN Not. 1986;21(11):406–16.CrossRefGoogle Scholar

Copyright information

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

Authors and Affiliations

  1. 1.Arizona State UniversityPhoenixUSA

Section editors and affiliations

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