Subject: new glossary entries

From: [email-masked] (Angelo Montanari)
Date: Mon, 31 May 93 09:50:09 +0100

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\section*{New glossary entries}

To the TSQL group,

\noindent
please find enclosed some new glossary entries. We would like to acknowledge
the contributions of Curtis Dyereson to their clarification and refinement
by several e-mail discussions. Part of them are revised versions of entries
we proposed in previous messages, namely, temporal qualification,
chronologically definite, chronologically indefinite, absolute time, relative
time. We hope that we can definitively agree about them. Part of them modify or
integrate existing glossary entries, namely instant, event, event occurrence
time, interval, interval relation, interval relation holding time, macro-event.
We believe that they require a general discussion.

\subsection{Instant}

\entry{Definition}

An instant is a point on the time axis. It belongs to a single chronon {\sl t}.
Many instants could belong to the same chronon. All the instants that belong
to a chronon are represented by that chronon. 

\entry{Alternative Names}

Event, moment.

\entry{Discussion}

``Event'' is often given a different meaning (-E5), while ``moment'' my be
confused with the distinct term ``chronon'' (-E7).

\subsection{Event}

\entry{Definition}

An event is an instantaneous fact, i.e. something occurring at an instant.
An event is said to occur at a chronon {\sl t} if it occurs at any instant 
during {\sl t}.

\entry{Alternative Names}

Event relation, instant relation.

\entry{Discussion}

``Event relation'' is not consistent with the distinction between ``instant'' 
and ``event'' (-E7). ``Instant relation'' is longer than event (-E2).

\subsection{Event occurrence time}

\entry{Definition}

The event occurrence time is the instant at which the event occurs 
in the real-world. The valid time associated with the event is the chronon {\sl
t} to which the event occurrence time belongs.

\entry{Alternative Names}

Event time.

\entry{Discussion}

Event occurrence time is more precise than event time (+E9). Nevertheless, when
the context is clear, the event occurrence time may be shorthened to the event
time.

\subsection{Interval}

\entry{Definition}

An interval is the time between two instants. It may be represented by a set of
contiguous chronons.

\entry{Alternative Names}

Time period.

\entry{Discussion}

The name ``interval'' is widely accepted (+E3). The name ``period'' often
implies a cyclic or recurrent phenomenon (-E8,-E9). In addition, ``time
period'' is longer (-E2).

\subsection{Interval relation}

\entry{Definition}

An interval relation is a (non-wholistic) fact with duration. An interval
relation is said to hold over an interval {\sl I} if it holds at all time
instants belonging to the set of contiguous chronons representing {\sl I}.

\entry{Alternative Names}

\entry{Discussion}

\subsection{Interval relation holding time}

\entry{Definition}

The interval relation holding time is the set of contiguous instants 
over which the interval relation holds in the real-world.
The valid time interval associated with the interval relation is the pair
consisting of the starting and the ending chronons.

\entry{Alternative Names}

Interval relation time.

\entry{Discussion}

Interval relation holding time is more precise than interval relation time 
(+E9). Nevertheless, when the context is clear, the interval relation holding
time may be shorthened to the interval relation time.

\subsection{Macro-Event}

\entry{Definition}

A macro-event is a wholistic fact with duration, i.e. something occurring
over an interval taken as a whole. A macro-event is said to occur over an
interval {\sl I} if it occurs over the set of contiguous chronons representing
{\sl I} (considered as a whole).

\entry{Alternative Names}

Process.

\entry{Discussion}

``Process'' is an over-loaded term, that is, a term having quite different
meanings in different contexts (-E9).

Examples of macro-events are baking a cake, having a dinner party, flying from
Rome to Paris.

It is worth remarking the distinction between macro-events and interval
relations. Saying that a macro-event relates to the structure of an interval as
whole means that if it consumes a certain interval it cannot possibly transpire
during any subinterval thereof.

\subsection{Temporal Qualification}

\entry{Definition}

The temporal qualification of a statement is  the component of the statement
that specifies the temporal localization  of the denoted fact, namely, an
associated instant, span, or interval. 

\entry{Alternative Names}

Time specification.

\entry{Discussion}

We assume one temporal qualification per statement. Moreover, we assume that
implicit temporal  qualifications  (e.g. tense qualifications) are  always made
explicit. As an  example, we assume  that the statement  ``They went to 
Arlington'' is  rewritten as ``Sometimes in the past is true  that they {\em go}
to Arlington''. Finally, if the temporal qualification is absent or missing
the default qualification is the current time ``now''. 

We distinguish between two different types of temporal qualifications, namely,
chronologically definite and indefinite temporal qualifications. 

\subsection{Chronologically definite temporal qualification}

\entry{Definition}

Chronologically definite temporal qualifications are specifications
of absolute temporal positions.

\entry{Alternative Names}

\entry{Discussion}

Examples are: June 15, 1993 (dates), 397 years after the discovering of America.
The notion of chronologically definite temporal qualification is different from
the notion of absolute time. Consider the case of temporal qualifications
relating the occurrence time of an event to the occurrence time of another event
rather than to the current (implicit) time {\em now}. Even if they can be
considered relative times, they are chronologically definite. They specify  an
absolute temporal position which may possibly be unknown  (it depends on common
sense as well as context knowledge). Examples of statements including these
kinds of chronologically definite temporal qualifications are: ``the French
revolution  occurred 397  years after  the discovering of America'', ``Mary's 
salary was raised  before Lucy's''.  

\subsection{Chronologically indefinite temporal qualification}

\entry{Definition}

Chronologically indefinite temporal qualifications are specifications
of temporal positions in terms of displacements with respect 
to the current time ({\em now}) which is left implicit.

\entry{Alternative Names}

\entry{Discussion}

The notion of chronologically indefinite temporal qualification is different
from the notion of relative time as shown in the related discussion about
chronologically definite temporal qualifications. Examples are: tomorrow,
three days ago, next month. 

\subsection{Chronologically Definite}

\entry{Definition}

Chronologically definite statements are statements whose truth 
value does not vary, because it does not depend on the time at 
which they are evaluated. Chronologically definite statements
are characterized by chronologically stable temporal qualifications.

\entry{Alternative Names}

\entry{Discussion}

Examples are: ``Jack was killed on xx/xx/1990'', it happened sometime in 1999'',
``the Jurassic is sometime after the Triassic'', ``the French revolution 
occurred 397 years after the discovering of America''.

In particular, consider the statement ``the French revolution 
occurred 397 years after the discovering of America'', where 
the occurrence time of ``the French revolution'' is given with 
respect to the occurrence time of ``the discovering of America''  
by means of the temporal qualifier ``397 years after'' (relative 
time). This statement is chronologically definite, because its 
truth value does not depend on the time at which it is evaluated. 

\subsection{Chronologically Indefinite}

\entry{Definition}

Chronologically indefinite statements are statements whose truth 
value may vary, because it depends on the time at which they are 
evaluated. Chronologically indefinite statements are characterized
by chronologically unstable temporal qualifications or are devoid
of any temporal qualification (a statement with no temporal 
qualification is equivalent to a statement characterized by a zero
displacement with the respect to the implicit current time).

\entry{Alternative Names}

\entry{Discussion}

Examples are: ``Mary's salary was raised yesterday'', ``it happened sometime
last week'', ``it happened on Easter'', ``it happened within 3 days of 
Easter''.

\subsection{Absolute time}

\entry{Definition}

Modifier indicating that a specific valid time at a given time-stamp granularity
is associated with a fact. Such a time depends neither on the valid time of
another fact nor on the current time now.

\entry{Alternative Names}

\entry{Discussion}

Examples are: ``Mary's salary was raised on March 30, 1993'', ``Jack was killed
on xx/xx/1990''.

Notice that absolute times are associated with chronologically definite 
statements only.

\subsection{Relative time}

\entry{Definition}

Modifier indicating that the valid time of a fact is related to either the valid 
time of another fact or the current time now.

\entry{Alternative Names}

\entry{Discussion}

The relationship between times can be qualitative (before, after, etc.) as well
as quantitative (3 days before, 397 years after, etc.).

Examples are: ``Mary's salary was raised yesterday'', ``it happened sometime
last week'', ``it happened within 3 days of Easter'', ``the Jurassic is sometime
after the Triassic'', ``the French revolution  occurred 397 years after the
discovering of America''.

Notice that both chronologically indefinite and definite statements can involve
relative times.

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\noindent
Comments are welcome

\vskip0.5cm
\noindent
Angelo Montanari, Elisa Peressi, Barbara Pernici

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Dipartimento di Matematica e Informatica
Via Zanon, 6
33100 Udine (Italy)
ph. +39 432 272 218/206
fax +39 432 510755
[email-masked] / [email-masked]
[email-masked]   / [email-masked]
[email-masked]
\end{verbatim}

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