A Simple Approach To Temporal Data In
Relational DBMS
Author(s)
M. K. Crowe
Abstract
Recent articles and research issues suggest that temporal data remains a source of
difficulty to database designers and implementers.
This paper analyses some of the issues and suggests some mechanisms that
could help simplify the problems, notably a new derived column concept for
NEXT, a new temporal join operator and temporal predicates CURRENT and
AT. However, the suggestions avoid adding any new data types or table types
and the language extensions are in the spirit of the SQL standard. The paper
includes full details of the proposed specification of these functions in the style
of the SQL standard. These specifications are implemented in version 1.2 of the
Pyrrho DBMS, an (otherwise) SQL-2003 compliant relational DBMS.
Keywords: temporal data, DBMS, relational database, fold, interleave.
1 Introduction
Zimanyi [2] includes in his paper an excellent introduction to the history of the
SQL/Temporal proposal, and how it did not find a place in as Part 7 of SQL2003
[4], and his article contains numerous examples of temporal data and excellent
accounts of how temporal manipulations of such data can be effected using
standard SQL.
He largely follows the original approach of Snodgrass [5] and the proposed
SQL/Temporal language in defining a temporal database table as one in which
there is one or two added pairs of columns FromDate and ToDate (when two
pairs are added one is for \“valid time” and the other for \“transaction time”). This
approach has been criticised as misconceived by Date et al [6]: certainly it seems
an overly mechanistic approach to a series of subtle semantic problems (Gabbay
and McBrien [7]).
Keywords
temporal data, DBMS, relational database, fold, interleave.
Related Book
Other papers in this volume
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