Encyclopedia of Database Systems

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

Temporal Expression

  • Christian S. Jensen
  • Richard T. Snodgrass
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1420

Definition

A temporal expression is a syntactic construct used, e.g., in a query that evaluates to a temporal value, i.e., an instant, a time period, a time interval, or a temporal element.

Key Points

Advanced by Gadia [1], a temporal expression is a convenient temporal query language construct.

First, any temporal element is considered a temporal expression. As Gadia uses a discrete and bounded time domain, any subset of the time domain is then a temporal expression. Next, an attribute value of a tuple in Gadia’s data model is a function from the time domain to some value domain. Likewise, the attribute values of a tuple are valid during some temporal element. To illustrate, consider an (ungrouped) relation with attributes Name and Position. An example tuple in this relation is:
$$ \begin{array}{l} \left(\left\langle \left[4;\;17\right]\; Bill\right\rangle,\;\left\langle \left[4;\;8\right] Assistant,\right.\right.\\ \quad \left.\left. \left[9;\;13\right]\;...
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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