Valid Time Selection And Projection In Tsql2
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The TSQL2 Temporal Query Language
Author: Richard T. Snodgrass
language: en
Publisher: Springer Science & Business Media
Release Date: 2012-12-06
Temporal databases have been an active research topic for at least fifteen years. During this time, several dozen temporal query languages have been proposed. Many within the temporal database research community perceived that the time had come to consolidate approaches to temporal data models and calculus based query languages, to achieve a consensus query language and associated data model upon which future research can be based. While there were many query language proposals, with a diversity of language and modeling constructs, common themes kept resurfacing. However, the community was quite frag mented, with each research project being based on a particular and different set of assumptions and approaches. Often these assumptions were not germane to the research per se, but were made simply because the research required a data model or query language with certain characteristics, with the partic ular one chosen rather arbitrarily. It would be better in such circumstances for research projects to choose the same language. Unfortunately, no existing language had attracted a following large enough to become the one of choice. In April, 1992 Richard Snodgrass circulated a white paper that proposed that a temporal extension to SQL be produced by the research community. Shortly thereafter, the temporal database community organized the "ARPA/NSF In ternational Workshop on an Infrastructure for Temporal Databases," which was held in Arlington, TX, in June, 1993.
Valid-time Selection and Projection in TSQL2
Abstract: "Temporal databases have now been studied for more than a decade. During that period of time, numerous query languages have been proposed for temporal databases. One of the essential components of a temporal query language is valid-time selection, which allows the user to retrieve tuples according to their valid-time relationship. Often, this component is closely tied to another important component, valid-time projection, which defines the timestamps of the tuples in query results. Here, nine different temporal query languages, primarily SQL and QUEL extensions, are examined with a focus on valid-time selection and projection. Based on that survey, the specific design of the valid-time selection and projection components of the consensus temporal query language TSQL2 are presented."
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