Subject: glossary

From: "Rick Snodgrass" <rts>
Date: Wed, 10 Mar 1993 09:18:04 MST

Christian's definitions used several terms that haven't been defined.
Below are candidate definitions for these new terms. They are
straight-forward, except perhaps for bitemporal interval, which is
restricted to be a rectangle.

{\em chronon} and {\em event} should be added to the list of nouns
that {\em valid-time}, {\em transaction-time}, and {\em bitemporal}
can modify.

\subsection{Valid-time Interval}

\entry{Definition}

A {\em valid-time interval} is an interval along the valid time-line.
It identifies when some fact was true in reality.

\entry{Alternative Names}

None.

\entry{Discussion}

A valid-time interval can be represented with a contiguous, non-empty set of
valid-time chronons.

\subsection{Transaction-time Interval}

\entry{Definition}

A {\em transaction-time interval} is an interval along the transaction
time-line. It identifies when a fact was logically in the database,
from the time it was inserted until the time it was logically deleted.

\entry{Alternative Names}

None.

\entry{Discussion}

A transaction-time interval can be represented with a non-empty set of
contiguous transaction-time chronons.

\subsection{Bitemporal Interval}

\entry{Definition}

A {\em bitemporal interval} is a region in two-space of
valid time and transaction time, with sides parallel to the axes. It
identifies when a fact, recording
that something was true in reality during the specified interval of
valid time, was logically in the database during the specified
interval of transaction time.

\entry{Alternative Names}

None.

\entry{Discussion}
A bitemporal interval can be represented with a set of bitemporal
chronons.