Encyclopedia of Database Systems

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

Time Instant

  • Christian S. JensenEmail author
  • Richard T. Snodgrass
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1516


Moment; Time point


A time instant is a single, atomic time point in the time domain.

Key Points

Various models of time have been proposed in the philosophical and logical literature of time. These view time, among other things, as discrete, dense, or continuous.

Instants in the dense model of time are isomorphic to the rational numbers: between any two instants there is always another. Continuous models of time are isomorphic to the real numbers, i.e., they are dense and also, unlike the rational numbers, without “gaps.”

A discrete time domain is isomorphic to (a possibly bounded subset of) the natural numbers, and a specific instant of such a domain then corresponds to some natural number.

The elements of a discrete time domain are often associated with some fixed duration. For example, a time domain can be used where the time elements are specific seconds. Such time elements are often called chronons. In this way, a discrete time domain can approximate a dense or...

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Recommended Reading

  1. 1.
    Bettini C, Dyreson CE, Evans WS, Snodgrass RT, Wang XS. A glossary of time granularity concepts. In: Etzion O, Jajodia S, Sripada S, editors. Temporal databases: research and practice, LNCS, vol. 1399. Berlin: Springer; 1998. p. 406–13.CrossRefGoogle 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. LNCS, vol. 1399. 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