Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!columbia!rutgers!ames!ptsfa!ihnp4!homxb!houxm!mtuxo!mtgzz!bds
From: bds@mtgzz.UUCP
Newsgroups: comp.ai
Subject: Re: English grammar (was Re: In layman's terms.)
Message-ID: <2704@mtgzz.UUCP>
Date: Thu, 28-May-87 15:28:26 EDT
Article-I.D.: mtgzz.2704
Posted: Thu May 28 15:28:26 1987
Date-Received: Sat, 30-May-87 08:19:07 EDT
References: <13263@watmath.UUCP> <1116@houdi.UUCP> <2112@husc6.UUCP>
Organization: AT&T, Middletown NJ
Lines: 32
Keywords: English, Backus-Naur Form, syntax.
Summary: context sensitive != ambiguous

In article <2112@husc6.UUCP>, hughes@endor.harvard.edu (Brian Hughes) writes:
> 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

	What I've seen in the literature is a definite trend towards
considering English as context free. I think it was Patrick Winston who
wrote in his AI text that examples of context sensitive English were
really examples of ambiguous English. Context free parsing algorithms
can handle ambiguous grammars, and in fact a BNF like formalism for
parsing English was done in the LSP system (described in a book I don't
have handy right now). The ambiguity in parses were
resolved through a "restriction language" which was essentially a
set of rules that avoided invalid parses (this is analogous to how many
C compilers handle parsing of "lvalues" - the grammar just knows about
expressions, the semantics worry about the "lvalue" quality).
The LSP grammar for English was quite large (but so are the ATNs; take
a peek at the one for LUNAR!) and was still evolving even as the book was
written. Still the issue has not been resolved to my knowledge.
	It's also worth while to look at some work being done
with WASP systems (aka Marcus parser - see Winston's AI book again).
There are serious arguments that WASP systems model human parsing of
English, and is being used as a basis for theories on how English is
learned (see "Acquisition of Syntactic Knowledge", by R.C. Berwick;
MIT Press 1985).