Encyclopedia of Database Systems

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

User-Defined Time

  • Christian S. Jensen
  • Richard T. Snodgrass
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1065

Definition

The concept of user-defined time denotes time-valued attributes of database items with which the data model and query language associate no special semantics. Such attributes may have as their domains all domains that reference time, e.g., date and time. The domains may be instant-, period-, and interval-valued. For example, user-defined time attributes include “birthday,” “hiring date,” and “contract duration.” Thus, user-defined time attributes are parallel to attributes that record, e.g., salary, using domain “money” and publication count, using domain “integer.” User-defined time attributes contrast transaction-time and valid-time attributes, which carry special semantics.

Key Points

The valid time and transaction time attributes of a database item are “about” the other attributes of the database item. The valid time records when the information recorded by the attributes is true in the modeled reality, and the transaction time captures when the data item was part of the...

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Recommended Reading

  1. 1.
    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
  2. 2.
    Snodgrass RT, Ahn I. A taxonomy of time in databases. In: Proceedings of the ACM SIGMOD International Conference on Management of Data. 1985. p. 236–46.Google Scholar
  3. 3.
    Snodgrass RT, Ahn I. Temporal databases. IEEE Comput. 1986;19(9):35–42.zbMATHCrossRefGoogle 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