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Time and Relational Theory, 2nd Edition
book

Time and Relational Theory, 2nd Edition

by C.J. Date, Hugh Darwen, Nikos Lorentzos
August 2014
Advanced content levelAdvanced
560 pages
15h 32m
English
Morgan Kaufmann
Content preview from Time and Relational Theory, 2nd Edition
Chapter 17

Logged Time and Stated Time

This chapter takes a much closer look at two concepts originally introduced in Chapter 4, viz., “valid time” and “transaction time.” Valid time has to do with when we believe (explicitly or implicitly) that some proposition is, was, or will be true. Transaction time has to do with when the database said (explicitly or implicitly) that we believe (again, explicitly or implicitly) that some proposition is, was, or will be true. Valid times are maintained—at least in a relational system—just like any other kind of data; in particular, they’re updatable just like any other kind of data. By contrast, transaction times are maintained by the system; in particular, therefore, they’re read-only (at least from the ...

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Publisher Resources

ISBN: 9780128006313