CCAT: TIME mission & tenses (Fritz Lehmann)
Date: Mon, 10 Oct 94 20:22:40 CDT
From: (Fritz Lehmann)
Message-id: <>
Subject: CCAT: TIME mission & tenses
Cc:, anquetil@IRO.UMontreal.CA,,,,,,,,,,,,,,,,, kivs@bgcict.bitnet,,,,,,,,,,,,,,
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     Bernard Moulin wrote to the CCAT people:
>From: (Bernard Moulin)
>Subject: CCAT  time and STATE requirements
>Hi Fritz,
>Can I join this list.

      Yes, Bernard, I've put you on the CCAT list.  Please note that it
is not a listserver email list, just an informal list of names of people
interested in CCAT (Conceptual Catalogues/Ontologies group of the Peirce
Project).  Members: please add to your CCAT copy-to

>I am sure you are aware that linguists have proposed
>various ontologies for expressing temporal concepts. This is especially
>important to express the semantics of verb tenses. Among various proposals
>there are different kinds of distinctions of states, events, processes
>and sub-categories. See the works by Vendler, Dowty, Passonneau, Moens and
>Steedman, Descles, etc.

     I'm not aware of the differences between these systems.  The first
thing you can do as a CCAT member is to send us a short list of the
issues and differences which you consider important, and your own
preference.  Also send a list of the predicates and relations (like
"BEFORE", etc.) which your compound-tense-systems would expect an
underlying TIME ontology to provide.  Pat Hayes has a base-level
ontology for time (actually a set of them) which we hope to place in
service of higher-level time systems; he will be able to tell us if his
proposed ontology can supply your list of needed relations.  He has
already told us that indexicality will _not_ be in the TIME ontology, so
you will need some other source for the indexicality of "now" and of
"then".  The issue of indexicality (referring to something by its
relation to oneself) is one of the, if not the, deepest issues in
philosophy, and anyone is free to suggest how CCAT should handle it.
Pat is right to say that logic does not cover the notion of
indexicality. It lacks a definable predicate meaning "I am" (compare
Genesis 2:14).

>There is also Barwise's Situation Semantics which provides a certain
>interpretation of situations in relation with time.

     Briefly, how does Sitation Semantics handle time?  Should CCAT
follow this line?  I'm hoping that John Sowa will decide what his
current view of situations is and disclose this to the CCAT group.
SITUATIONS is one of the "core ontologies" of CCAT but no-one has
offered any ideas on what should be in it.  Sowa and Bill Tepfenhart in
the conceptual graphs community have opined on situation theory in the
past.  At present CCAT has nothing on SITUATIONS.

>I have not followed your discussions from the beginning, so I don't know
>what are the precise objectives of the CCAT group on time and STATE
>requirements.      I hope that this information will be a useful
>contribution to the discussion.

     Bernard, your views are needed.  I have already mentioned your work
on compound tenses a few times.  Having dealt with the practicalities,
you are in the best position to present Hayes with a list of the time-
predicates which will be needed for a versatile tense system.

     The precise objectives now of CCAT/TIME are to have a base-level
axiomatization of time (or nearly interchangeable set of axiomatizations)
which has pre-defined predicates and relations needed by higher time-
systems such as digital timing systems, compound tense systems,
communicating processes, and international standards for calendars, dates
and times.  Pat Hayes is doing the low-level axiomatizations of time, and
Walling Cyre has provided a poset of time relations which will be needed
for digital circuits.  Hayes is expected (we hope) to satisfy you and
Cyre and me (and others who demand things of time) while remaining true
to his logicist approach.  As soon as a consistent, servicable time
ontology is available (based now on Hayes' base-ontology, plus the
defined predicates and relations you and the rest of us ask for), it will
be placed in a CCAT/TIME FTP site for use and feedback.  Hayes will
probably express it in FOL, HOL or KIF  As soon as the KIF-CG mapping is
firmed up, we will put the CG version of Hayes' ontology into the CCAT
"core" -- until and unless some other candidates for the TIME ontology
emerge.  Any generally useful extensions which are not inconsistent with
the base-ontology can also be added to the core.  (TIME ontologies
inconsistent with Hayes can also be in the CCAT FTP site, but not in the
official "core" for now.)  One of our biggest problems is to decide upon
one of the many possible systems of _approximation_ for time and for
other areas.  If you say an airplane took off at noon, your statement
usually should not be rendered false by its having taken off at 11:59.59
a.m.  The ARPA Rome Planning Ontology has a method for allowing this.

     As for STATE, that's under the CCAT OBJECT/EVENT/PROCESS subgroup
and it's the subject of current discussion on email -- so far among
Hayes, Cyre, me and Allen Brewer with cc: to the CCAT list.  This is
intimately connected with TIME.  OBJECT/EVENT/PROCESS is one of the
hardest areas to figure out acceptably.  There are a surfeit of books and
opinions on the subject.  CCAT somehow needs to navigate these waters.

                          Yours truly,   Fritz Lehmann
GRANDAI Software, 4282 Sandburg Way, Irvine, CA 92715, U.S.A.
Tel:(714)-733-0566  Fax:(714)-733-0506