Encyclopedia of Database Systems

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

Time Period

  • Nikos A. Lorentzos
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1425

Synonyms

Time interval

Definition

If the time domain is a totally ordered set T = {t1, t2, t3…} then a time period over T is defined as a convex subset of elements from T.

Example: If T = {d1, d2, d3,…}, where di are consecutive dates, then [d10, d20] and [d30, d80] represent two time periods over T.

Key Points

In the area of temporal databases, a time period over T is usually defined as a distinct data type. Some researchers define a time period data type of the form [tp, tq]. Some others define such a data type of the form [tp, tq), i.e., its right end is closed.

Note that, initially, the term time interval was used instead of time period. This was later abandoned in order to avoid confusion, given that interval is a reserved word in SQL. Instead, time interval in today used with a different meaning (see time interval).

Cross-References

Copyright information

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

Authors and Affiliations

  1. 1.Informatics Laboratory, Department of Agricultural Economics and Rural DevelopmentAgricultural University of AthensAthensGreece

Section editors and affiliations

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