John
as you are being so kind to spell it out for us in plain language... (01)
what is the accepted syntax for pTim
can pTim be a timestamp? is there a prescribed format for time/date in ikl (02)
thanks
P (03)
On Jan 21, 2008 2:18 PM, John F. Sowa <sowa@xxxxxxxxxxx> wrote:
> John B.,
>
> Some answers to your questions:
>
> > 1. Is the interpretation of [Proposition: p'] true if p' is true
> > and false otherwise?
>
> Actually, it's more primitive than that. It's true if p' is a
> proposition and false if p' is not a proposition.
>
> In effect, a conceptual graph g is true or false by itself (just
> as any formula in any version of logic). But when you surround
> g by a box with a type label, the only thing that is asserted
> is that g is of that type. (If it's not of that type, as in
> [Situation: g], then type coercion causes g to be interpreted
> as a statement of a proposition that describes the situation.)
>
> That corresponds to what the QUOTE operator does in Lisp: it
> prevents the following expression from being evaluated. In order
> to force the evaluation in Lisp, it's necessary to use another
> operator called EVAL:
>
> (EVAL (QUOTE s)) is equivalent to s by itself.
>
> In conceptual graphs, the Asrt (assert) relation has that effect:
>
> (Asrt [Proposition: g]) is equivalent to writing g by itself
> on a 'sheet of assertion' (Peirce's term).
>
> > 2. What about the [Situation *s] graph? This is true if there
> > in fact existed a situation on 20 January 2008 that made
> > proposition p' true?
>
> That concept node, by itself, simply says that there exists a
> situation, and s is used to label it. It maps to the following
> formula in CLIF:
>
> (exists (s) (Situation s))
>
> To say that there existed a situation on that date that made p' true,
> you would write
>
> [Situation: *s p'] (PTim ?s "20 January 2008")
>
> By type coercion, the concept node on the left would be expanded:
>
> [Situation: *s] [Proposition: *x p'] (Dscr ?s ?x)
> (PTim ?s "20 January 2008")
>
> This says that there exists a situation s, there exists a proposition x
> stated by the graph p', the description of s is x, and the point in time
> of s is 20 January 2008. Following is the corresponding IKL:
>
> (exists (s x) (and (Situation s) (Proposition x) (= x (that p))
> (Dscr s x) (PTim s "20 January 2008"))
>
> > 3. In the context framework you mentioned the other day, with the
> > triples, you defined (T1,X,T2) as a T1 = a bounded text, X = a
> > context, and T2 = axioms showing the relation of T1 to X.
> > What would be an example of an axiom that relates p' to
> > (PTim ?s, "20 January 2008")? Does this simple example need any?
>
> The graph p' would correspond to the text T1. The situation s would
> be the context X, in terms of which the T1 is interpreted. The text
> T2 would be some axioms stated in some version of logic (which could
> be stated in conceptual graphs, IKL, or any other suitable notation)
> that would say how the PTim relation is supposed to relate any
> situation to any date (of which s and "20 January 2008" are examples).
>
> John Sowa
>
>
>
>
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> (04)
--
Paola Di Maio
School of IT
www.mfu.ac.th
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