Subject: Proposed Glossary Entry

From: Jim Clifford <[email-masked]>
Date: Wed, 28 Apr 93 16:23:33 EDT

With the deadline approaching, I noticed that some term distinguishing
what we have called grouped and ungrouped models appears to be
necessary. The following proposal is for a term that attempts to
characterize what I (along with Al Croker and Alex Tuzhilin) see as the
major difference -- on a semantic level, without being too
model-specific-- between these two approaches. It is basically taken
from our CCT paper (reduced version in the Temp Databases book).

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\begin{document}

\subsection{Temporal Value Integrity}

\entry{Definition}         

A temporal DBMS is said to have {\em temporal value integrity} if:

\begin{enumerate}

\item The integrity of temporal values as first-class objects is inherent 
in the model, in the sense that the language provides a mechanism
(generally, variables and quantification) for direct reference to {\em
value histories} as objects of discourse, and

\item Temporal values are considered to be
{\em value equivalent} only if they are equal for all points in time
over which they are defined.

\end{enumerate}

\entry{Alternative Names}   

None.

\entry{Discussion}

The concept of {\em temporal value integrity} provides a term for the
characteristic distinguishing those models which represent {\em time}
as just another attribute or set of attributes, from those which
represent temporal values directly.  The former models do not have a
primitive notion of a temporal value.  Instead, they have the
primitive notions of time values and ordinary values, and they can
represent associations between these two types of values, for example,
they can represent the (non-temporal) {\em value of a SALARY at time
t}. Those models with {\em temporal value integrity} have built in the
primitive notion of a temporal value.  In these models one can refer
to a primitive temporal value like a {\em SALARY history}, as well as
referring to the (non-temporal) {\em value of a SALARY history at time
t}.

The orthogonality criterion (+E1) is satisfied, and there are no
competing names in the literature (+E3), and the term does not appear
to have other meanings (+E5). Further, the name is consistent with
existing terminology (+E7) (and, indeed, clarifies the meaning of the
term {\em value equivalence}, and does not violate other criteria.

\end{document}