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Temporal Coalescing

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Encyclopedia of Database Systems

Definition

Temporal coalescing is a unary operator applicable to temporal databases that is similar to duplicate elimination in conventional databases. Temporal coalescing merges value-equivalent tuples, i.e., tuples with overlapping or adjacent timestamps and matching explicit attribute values. Tuples in a temporal relation that agree on the explicit attribute values and that have adjacent or overlapping timestamps are candidates for temporal coalescing. The result of operators may change if a relation is coalesced before applying the operator. For instance, an operator that counts the number of tuples in a relation or an operator that selects all tuples with a timestamp spanning at least 3 months are sensitive to temporal coalescing.

Historical Background

Early temporal relational models implicitly assumed that the relations were coalesced. Ben Zvi’s Time Relational Model [13, Chap. 8], Clifford and Croker’s Historical Relational Data Model (HRDM) [13, Chap. 1], Navathe’s Temporal...

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Author information

Authors and Affiliations

  1. Free University of Bozen-Bolzano, Bolzano, Italy

    Michael Böhlen

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  1. Michael Böhlen
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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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Böhlen, M. (2009). Temporal Coalescing. In: LIU, L., ÖZSU, M.T. (eds) Encyclopedia of Database Systems. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-39940-9_388

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