Encyclopedia of Database Systems

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

Temporal Homogeneity

  • Christian S. Jensen
  • Richard T. Snodgrass
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1421

Definition

Assume a temporal relation where the attribute values of tuples are (partial) functions from some time domain to value domains. A tuple in such a relation is temporally homogeneous if the domains of all its attribute values are identical. A temporal relation is temporally homogeneous if all its tuples are temporally homogeneous. Likewise, a temporal database is temporally homogeneous if all its relations are temporally homogeneous.

In addition to being specific to a type of object (tuple, relation, database), homogeneity is also specific to a time dimension when the time domain is multidimensional, as in “temporally homogeneous in the valid-time dimension” or “temporally homogeneous in the transaction-time dimension.”

Key Points

The motivation for homogeneity arises from the fact that no timeslices of a homogeneous relation produce null values. Therefore, a homogeneous relational model is the temporal counterpart of the snapshot relational model without nulls. Certain data...

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Recommended Reading

  1. 1.
    Gadia SK. A homogeneous relational model and query languages for temporal databases. ACM Trans Database Syst. 1988;13(4):418–48.MathSciNetzbMATHCrossRefGoogle Scholar
  2. 2.
    Jensen CS, Dyreson CE, editors. A consensus glossary of temporal database concepts – February 1998 version. In: Etzion O, Jajodia S, Sripada S, editors. Temporal databases: research and practice. Berlin: Springer; 1998. p. 367–405.Google Scholar

Copyright information

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

Authors and Affiliations

  1. 1.Department of Computer ScienceAalborg UniversityAalborgDenmark
  2. 2.Department of Computer ScienceUniversity of ArizonaTucsonUSA
  3. 3.Dataware VenturesTucsonUSA

Section editors and affiliations

  • Richard T. Snodgrass
    • 1
  • Christian S. Jensen
    • 2
  1. 1.University of ArizonaTucsonUSA
  2. 2.Aalborg UniversityAalborg ØstDenmark