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From: hughes@endor.harvard.edu (Brian Hughes)
Newsgroups: comp.ai
Subject: Re: English grammar (was Re: In layman's terms.)
Message-ID: <2112@husc6.UUCP>
Date: Wed, 27-May-87 23:19:36 EDT
Article-I.D.: husc6.2112
Posted: Wed May 27 23:19:36 1987
Date-Received: Sat, 30-May-87 06:46:36 EDT
References: <13263@watmath.UUCP> <1116@houdi.UUCP>
Sender: news@husc6.UUCP
Reply-To: hughes@endor.UUCP (Brian Hughes)
Organization: Aiken Computation Lab Harvard, Cambridge, MA
Lines: 75
Keywords: English, Backus-Naur Form, syntax.

In article <1116@houdi.UUCP> marty1@houdi.UUCP (M.BRILLIANT) writes:
	(summarized)
>In article <13263@watmath.UUCP>, erhoogerbeet@watmath.UUCP writes:
>> ...
>> Is there a Backus-Naur Form for the English language itself or is this too
>> complicated? ... Basically, what I am asking is it possible to do syntactic
>> checking as if "compiling" a sentence with rules set down in some BNF?

	Natural language is not context free (though some people disagree
on this). BNF formalisms cannot deal with context sensitive languages

>About 30 years ago when I was at MIT doing graduate study in EE, my
>wife was talking with a guy named Chomsky who wanted to do machine
>translation.  The effort resulted in new approaches to English grammar,
>but not in machine translation.

	While in a strict sense this is true, Chomsky's transformational
grammer seems to be almost universaly accepted as the basis upon which to
build models that deal with the syntax of natural languages. This is true
for computerized models as well as pure abstract models.

>We read, write, talk, listen, understand and misunderstand each other
>in this chaos because our brains are not structured like computers.

	While I agree that my brain is not structured like an IBM/PC,
(at least IBM hasn't asked me for royalties :-)) or any existing silicon
processor, I don't agree with the implication that a computer cannot,
a priori, understand natural language. We just haven't built intelligent
enough systems yet (hardware & software architectures). I realize that
Marty Brilliant may not have meant the implication I read; just wanted
to make my position clear.

>> As I understand it so far, natural language processing would have at least
>> two levels (syntactic, semantic) and that syntactic checking level would
>> be the basis of the other.
>
>True.

	But that's not the end of the matter. You also have to deal with the
higher levels of language organization, such as discourse (e.g., a
conversation). An utterance may refer back to an entity introduced in a
previous utterance in "shorthand" - by a pronoun, or short refering expression.
To understand that shorthand, we somehow are able to (unconsciously) retrieve
the full referant. At an even higher level, a discourse may go from one
concept to a sub-concept, engage in temporary diversions, and jump from
one thing to another, but we can understand it. People are starting to
explicate the rules of discourse grammer, buts lots remains to be done.


>Seriously, I would like to know what (in plain English, if possible) is
>going on in formal English grammar and natural language parsing.

	For a nice, powerful method of parsing English into a deep
structure representation, check out ATNs (Augmented Transition Networks).
Bill Woods developed this method in the late 60's. You can implement a
simple ATN in a couple of pages of LISP (see Jon Amsterdam's article in
AI Expert a few months ago, also online in AI Expert's BBS). For a
full ATN writeup, including code, see The Lunar Sciences Natural Language
Information System: Final Report by W.A. Woods, R.M. Kaplan, and
B. Nash-Webber, BBN Report #2378, BBN, 50 Moulton St., Cambridge, MA.
Also see Madeline Bates' article "The Theory and Practice of Augmented
Transition Networks" in Natural Language Communications with Computers,
Bolc, L., ed., Springer-Verlag, 1978
	For a lot of different views of language understanding, all the
way from syntax through discourse, see Readings in Natural Language
Processing, Grosz, B., Jones, K.S., and Webber, B., eds., 1986,
Morgan Kauffman. After reading this, read a transcript of a naturally
occuring informal conversation to see how far we have yet to go.
	Please excuse the length of this - I just finished 2 courses
in this stuff with Bill Woods and Barbara Grosz, & its still buzzing
in my head.

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Disclaimer: Correct statements mainly due to profs. Woods & Grosz,
stupidities all my own.