Subject: temporal value integrity

From: "Rick Snodgrass" <rts>
Date: Fri, 30 Apr 1993 00:22:14 MST

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?