Encyclopedia of Database Systems

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

Forever

  • Christian S. Jensen
  • Richard T. Snodgrass
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1051

Synonyms

Infinity; Positive infinity

Definition

The distinguished value forever is a special valid-time instant, namely the one following the largest granule in the valid-time domain. Forever is specific to valid time and has no transaction-time semantics.

Key Points

The value forever is often used as the valid end time for currently-valid facts. However, this practice is semanticallys incorrect, as such an end time implies that the facts are true during all future times. This usage occurs because database management systems do not offer means of storing the ever-changing current time, now, as an attribute value. To fix the incorrect semantics, the applications that manipulate and query the facts may interpret the semantics specially. However, the better solution is to extend the database management system to support the use of the variable now as an attribute value.

Concerning the synonyms, “infinity” and “positive infinity” both appear to be more straightforward, but have conflicting...

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Recommended Reading

  1. 1.
    Jensen CS, Dyreson CE (eds.). A consensus glossary of temporal database concepts - February 1998 version. In: O. Etzion, S. Jajodia, S. Sripada, eds. Temporal databases: research and practice. Berlin/Heidelberg/New York: LNCS 1399, Springer; 1998. p. 367–405.Google Scholar
  2. 2.
    Torp K, Jensen CS, Snodgrass RT. Effective timestamping in databases. VLDB J. 2000;8(3–4):267–88.CrossRefGoogle 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