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Encyclopedia of Database Systems pp 3252Cite as

User-Defined Time

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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. 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. Jensen C.S. and Dyreson C.E. (eds.). A consensus glossary of temporal database concepts – February 1998 version. In Temporal Databases: Research and Practice, O. Etzion, S. Jajodia, S. Sripada (eds.). LNCS, vol. 1399, Springer-Verlag, Berlin, 1998, pp. 367–405.

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  2. Snodgrass R.T. and Ahn I. A taxonomy of time in databases. In Proc. ACM SIGMOD Int. Conf. on Management of Data, 1985, pp. 236–246.

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  3. Snodgrass R.T. and Ahn I. Temporal databases. IEEE Comput., 19(9):35–42, September 1986.

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Author information

Authors and Affiliations

  1. Aalborg University, Aalborg, Denmark

    Christian S. Jensen

  2. University of Arizona, Tucson, AZ, USA

    Richard T. Snodgrass

Authors
  1. Christian S. Jensen
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  2. Richard T. Snodgrass
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Editor information

Editors and Affiliations

  1. College of Computing, Georgia Institute of Technology, 266 Ferst Drive, 30332-0765, Atlanta, GA, USA

    LING LIU (Professor) (Professor)

  2. Database Research Group David R. Cheriton School of Computer Science, University of Waterloo, 200 University Avenue West, N2L 3G1, Waterloo, ON, Canada

    M. TAMER ÖZSU (Professor and Director, University Research Chair) (Professor and Director, University Research Chair)

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© 2009 Springer Science+Business Media, LLC

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Jensen, C.S., Snodgrass, R.T. (2009). User-Defined Time. In: LIU, L., ÖZSU, M.T. (eds) Encyclopedia of Database Systems. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-39940-9_1065

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