Encyclopedia of Database Systems

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

Time Span

  • Christian S. Jensen
  • Richard T. Snodgrass
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1429

Synonyms

Time distance; Time interval

Definition

A span is a directed duration of time. A duration is an amount of time with known length, but no specific starting or ending instants. For example, the duration “1 week” is known to have a length of 7 days, but can refer to any block of seven consecutive days. A span is either positive, denoting forward motion of time, or negative, denoting backwards motion in time.

Key Points

Concerning the synonyms, the terms “time interval” is generally understood to denote an anchored span in the general community of computer science. Only in the SQL language does “time interval” denote a span. The term “span,” which has only one definition, is thus recommended over “time interval” for works not related to the SQL language. This use is unambiguous.

A “duration” is generally considered to be non-directional, i.e., always positive. The term “time distance” is precise, but is longer.

Cross-References

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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 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 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