Re: [ontolog-forum] Requesting Opinions on the Benefits of Predicates as

[David Whitten <whitten@xxxxxxxxxx>]

I would like to point out that using July as a time is problematic,

as I believe that:

(cl:comment 'C employs P during time interval T'
        (employs C P July)
)

would say that July is a time interval.

To my way of thinking, July is the name of the (infinite) set

of all time intervals that can be classified as overlapping with

the month of July in any year.

Thus, the statement (employs IBM Fred July)

says that IBM employs Fred during the month of July in

every possible year. (perhaps Fred is a seasonal worker)

This is a different statement by far than saying IBM employs

Fred for a particular month of July in a particular year.

I expect also that the 3-D vs 4-D time view would argue

that it is actually a time-slice of Fred that is employed rather

than the Fred that exists at all times.

David Whitten

713-870-3834

On Tue, Jun 17, 2014 at 7:51 AM, Tara Athan <taraathan@xxxxxxxxx> wrote:

On 6/17/14 1:03 AM, Pat Hayes wrote:
>> Using the IKL “that” operator and a “during” relationship and the concept “July” (a ‘calendar month’):
> Whoa. No, this is NOT the right way to do it. In fact, this is meaningless. According to the IKL semantics, (that (employs C P)) denotes a fixed proposition which is true or false. There is no room for any time-dependent variability in its truth value, or for making it depend on some other parameter.
>

It may not be the *best* way to do it, but I don't agree that it's wrong
or meaningless. Using the proposition (that (employs C P)) as an
argument in a relation is not obstructed by its denotation of a fixed
proposition which is true or false (in any given interpretation).

Starting off without quantifiers:

(cl:comment 'C employs P'
    (employs C P) )

(cl:comment 'It holds during time interval T that C employs P'
    (during (that (employs C P)) T )

Nothing wrong with that - the truth values of these sentences are
independent of each other.

Now bring on the quantifiers to relate the two

(forall C P
   (if
     (cl:comment 'C employs P'
       (employs C P) )
     (exists T
(cl:comment 'It holds during some time interval T that C employs P'
         (during (that (employs C P)) T )
) ) )

Some users may find this clearer than the polymorphic representation.
Why not let them use it?
It is still possible to have the polymorphic representation behind the
scenes for reasoning purposes.
(forall C P T
   (iff
(cl:comment 'It holds during time interval T that C employs P''
        (during (that (employs C P)) T )
(cl:comment 'C employs P during time interval T'
        (employs C P T)
) )

Also, using the "that" operator for temporal context is a gateway to
using it for other contexts/modalities.
I find the symmetry appealing:
(cl:comment 'It holds before time interval T that C employs P'
    (before (that (employs C P)) T)
(cl:comment 'It holds after time interval T that C employs P'
    (after (that (employs C P)) T )
(cl:comment 'It is possible that C employs P'
    (possible (that (employs C P)) )
(cl:comment 'It is forbidden that C employs P'
    (forbidden (that (employs C P)) )
(cl:comment 'Jane believes that C employs P'
    (believes Jane (that (employs C P)) )
(cl:comment 'Omar knows that C employs P'
    (knows Omar (that (employs C P)) )
(cl:comment 'Maria asserts that C employs P'
    (asserts Maria (that (employs C P)) )
...

Tara

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