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From: ada612@csc.anu.oz.au
Newsgroups: comp.lang.prolog
Subject: Re: Question about DCG's and natural language
Message-ID: <1990Nov22.113849.3423@csc.anu.oz.au>
Date: 22 Nov 90 01:38:49 GMT
Organization: Computer Services, Australian National University
Lines: 33

Re: Message-ID: <MARK.90Nov21120114@adler.philosophie.uni-stuttgart.de>
    From: mark@adler.philosophie.uni-stuttgart.de (Mark Johnson)

>What's worrying me is this: if we use a DCG grammar to
>define a relation means/2 true of a string of English words
>and some representation of its meaning (say, an encoding of
>a first-order formula), we can prove things like the
>following:
>
>  S=[i,saw,a,man,with,a,telescope], means(S,M1), means(S,M2).
>
>where M1 represents a meaning where where the man has a telescope,
>and M2 represents a meaning where the seeing is done with the
>telescope.
>
>That is, from our axioms we can prove that S means M1 *and* S means M2.
>The problem is that in the real world it *doesn't*: the English sentence
>S means M1 *or* M2.

I would say that the correct reading of `means(X,Y)' is `sentence X
can have meaning Y', so that one sentence can have this relation to
several meanings, just like one person can have the `sister/2' relation
to several people.  For talking about particular situations, one might
want a three-place predicate `means(X,Y,S)' `sentence X had meaning Y
in (particular) situation S', where Y is supposed to be unique for
given X and S, but semioticists seem to differ on this kind of issue.

Presumably the and/or vagaries in the English renditions in the Horn clauses
arise from the the relations between the various senses of `mean', plus
modal logic & Cricean maxims.  e.g., it violates the maxim of quantity
to say `Possible(X or Y)' when `Possible(X) and Possible(Y)' isn't true.

  Avery Andrews (ada612@csc.anu.oz.au)