Encyclopedia of Database Systems

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

Time-Line Clock

  • Curtis E. DyresonEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1062


Baseline clock; Clock; Time-segment clock


In the discrete model of time, a time-line clock is defined as a set of physical clocks coupled with some specification of when each physical clock is authoritative. Each chronon in a time-line clock is a chronon (or a regular division of a chronon) in an identified, underlying physical clock. The time-line clock switches from one physical clock to the next at a synchronization point. A synchronization point correlates two, distinct physical clock measurements.

Key Points

A time-line clock is the clock for (concrete) times stored in a temporal database. A time-line clock glues together a sequence of physical clocks to provide a consistent, clear semantics for a time line. Since the range of most physical clocks is limited, a time-line clock is usually composed of many physical clocks. For instance, a tree-ring clock can only be used to date past events, and the atomic clock can only be used to date events since the 1950s....

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Recommended Reading

  1. 1.
    Dyreson CE, Snodgrass RT. Timestamp semantics and representation. Inf Syst. 1993;18(3):143–66.CrossRefGoogle Scholar
  2. 2.
    Dyreson CE, Snodgrass RT. The baseline clock. The TSQL2 temporal query language. Norwell: Kluwer; 1995. p. 73–92.Google Scholar
  3. 3.
    Fraser JT. Time: the familiar stranger. Amherst: University of Massachusetts Press; 1987. p. 408.Google Scholar

Copyright information

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

Authors and Affiliations

  1. 1.Utah State UniversityLoganUSA

Section editors and affiliations

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