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000031_rts _Wed Mar 10 09:18:04 1993.msg
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Received: from boojum.cs.arizona.edu by optima.cs.arizona.edu (5.65c/15) via SMTP
id AA17416; Wed, 10 Mar 1993 09:18:05 MST
Date: Wed, 10 Mar 1993 09:18:04 MST
From: "Rick Snodgrass" <rts>
Message-Id: <199303101618.AA24189@boojum.cs.arizona.edu>
Received: by boojum.cs.arizona.edu; Wed, 10 Mar 1993 09:18:04 MST
To: tsql@cs.arizona.edu
Subject: glossary
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.