Re: Comparing times in FOPC

On 23 Jun 2005 03:12:34 -0700, Gary Leighton <leightongary@xxxxxxxxxxx> said:
> My interest is in Natural Language Understanding and I am trying to
> find good representations using FOPC. I get into difficulties when I
> try to represent time and what I'd like to know is if FOPC is capable
> of doing this or whether there is a better logic language for the task.
>
> Here's an example of my problem:
>
> Ex,i Event(x)^Interval(x,i)^StartPoint(i,1998)^EndPoint(i,1999)
>
> This might be understood to mean "An event took place between 1998 and
> 1999"

That's a rather strange representation. First, assuming "Interval(x,i)"
means that event x occurs over interval i, one would think that 1998 is
itself an interval, not a point, hence it seems odd to say that it is
the start *point* of i. For the same reason, it also seems odd to talk
about an event occurring *between* 1998 and 1999, since they are
continguous; nothing is between them. Rather, it seems like you want to
say something like "i is between the beginning of 1998 and the end of
1999" or (depending on your primitives) "i is during the interval sum of
1998 and 1999". Such representations are available in the approach to
representing time developed in Allen and Hayes, "Moments and Points in
an Interval-based Temporal Logic." That framework is merged with a
basic theory of events in Allen and Ferguson, "Actions and Events in
Interval Temporal Logic." Both papes are available on the web. For a
very comprehensive overview of first- (and IIRC higher-) order
representations to time, see van Benthem, Logic and Time. See also
Hayes's "A Catalog of Temporal Theories,"
http://www.ihmc.us/users/phayes/docs/TimeCat96.pdf , a really nice
overview that also contains some novel work on clocks and calendars.

Chris Menzel

.

Relevant Pages

  • Re: Comparing times in FOPC
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  • Re: Comparing times in FOPC
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  • Comparing times in FOPC
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