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Subject: Re: anaphor means what? (was: oops! correction) 
In-Reply-To: Your message of "Thu, 25 Apr 91 10:23:38 BST."
             <"swan.cl.ca.187:25.03.91.09.23.53"@cl.cam.ac.uk> 
Date: Fri, 26 Apr 91 09:46:21 +0100
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X-From-Space-Date: Fri Apr 26 14:15:16 1991
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> Date:  Thu, 25 Apr 91 10:23:38 +0100
> To:  lojban-list@snark.thyrsus.com
> From:  David Elworthy <David.Elworthy@computer-lab.cambridge.ac.uk>
> Subject:  Re: anaphor means what? (was: oops! correction)
   
> ...interpreting anaphors by copying the words of the antecedent. This 
> is an approach which was suggested by linguists some time ago, and which
> has been firmly rejected. What is wrong with it? 

You need a commitment (which English doesn't give) that the copied words 
have the same referent in their new home.  In other words:

	Every farmer who owns (a donkey) beats (a donkey)  [must transform to]
	All F, ((F is a farmer) and (exists D) and (D is a donkey) and
		(F owns D)) implies (F beats D)		[the same D]

And similarly for other articles in extension (le, le'e).  In Lojban an
easy way to insure this is to define a sumti with <LE> to be 
an abbreviation for a restricted variable (da poi <bridi>), which 
unquestionably has the same referent everywhere it occurs in the sentence,
for each member of the sentence's Cartesian expansion.

Another requirement is that context, that is, implied tenses and the like,
is to be handled as if each selbri / sumti had an anaphor for each possible
tense or modal.  Thus if a tense determines referents, the same 
determination can be made in the copy.

Then, these anaphora and all others in the sumti would be filled in by 
copying, and only after that step would the sumti be copied (again and 
again) to fill up subsequent references to it.  

> The copying problem can also be seen in another classic sentence, 
> known as the Bach-Peters paradox:
> 
> (6) The boy who deserves it will get the prize he wants.

The infinite regression is a definite problem which I have already had to
solve by ugly hacks in [my] transformation program.  And even if referents 
are copied, not words, it looks to me as if you still have an infinite 
loop.  It reminds me of 

	(1 + x + x^2 + x^3 + ...) = 1/(1-x)

I wonder if a heavy logician could come up with the 1/(1-x) for this 
problem?  

> The conclusion from this is that the interpretation of anaphors is *not* 
> the business of the parser, or of the syntactic component in any sense. 

On that, I agree.  You have to do syntax analysis first, and do anaphor
resolution on its output.  Unfortunately and confusingly, in English 
you need semantic knowledge to straighten out the anaphora (and lots of
other syntactic features).  But that's because English is a pile of junk,
not an intrinsic feature of anaphora.

I would ascribe anaphor resolution to a "transformation" phase that
follows syntax analysis and precedes semantics.  My motivation is to
feed into the semantic analyser a uniform set of "deep structures".
Obviously :-), anaphora are irrelevant and have to be transformed away
first.  That is, "every farmer with a donkey beats IT" is semantically
identical to "every farmer with a donkey beats THE DONKEY" as well as to
the selected-by-me deep structure (all F|farmer exists D (D is donkey and
F owns D implies F beats D)).  

		-- jimc