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000097_rts _Fri Apr 30 00:22:14 1993.msg
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Received: from boojum.CS.Arizona.EDU by optima.CS.Arizona.EDU (5.65c/15) via SMTP
id AA19352; Fri, 30 Apr 1993 00:22:15 MST
Date: Fri, 30 Apr 1993 00:22:14 MST
From: "Rick Snodgrass" <rts>
Message-Id: <199304300722.AA11849@boojum.cs.arizona.edu>
Received: by boojum.cs.arizona.edu; Fri, 30 Apr 1993 00:22:14 MST
To: tsql@cs.arizona.edu
Subject: temporal value integrity
This definition is indeed a useful one. However, I think it needs some
refinement. (It was very helpful for Jim to put it in the recommended
format.)
1. It uses the term "temporal value" throughout, but never defines this
term. One could confuse it with timestamp (defined as a "time value
associated with an object"). Perhaps a separate definition of
this term would be useful.
2. It uses the term "value history," again without definition.
3. Value equivalence was previously defined. Is this definition also
providing a new definition for value equivalence, or is it
refining the definition when temporal value integrity is
present?
4. Does a DBMS or a data model have temporal value integrity? Or does
just a temporal query language have this property?
5. The discussion seems to equate "temporal value" with "value history"
("one can refer to a primitive temporal value like a
{\em SALARY history}"), as well as mentioning the "value of a
value history at time t" ("the (non-temporal) {\em value of
a SALARY history at time t}"). This is somewhat confusing. Even
more confusing is the term "{\em SALARY history}". Is this
in fact a value history? If so, then it would help if that were
stated explicitly.
I think that if these aspects were addressed, a more clear and useful
definition of this important concept would result.
Paolo, Fabio, and Maria, is there a connection with "temporal value"
and/or "value history" and your concept of a history variable?
Arie, is there a connection with "value history" and your concept of
a tuple sequence?
Should either of these terms be used instead? If not, would it be useful
to also define these terms for the glossary?