goldberg@su-russell.ARPA (Jeffrey Goldberg) (05/30/87)
In article <2112@husc6.UUCP> hughes@endor.UUCP (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 I don't think that there is any serious disagreement here. The work done by Culy on Bambara reduplication and Shieber on Swiss cross serial dependencies has convinced the last hold outs for CFness (Geoff Pullum, Gerald Gazdar, and their students: me, Culy, etc). >>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. These is hardly true at all. It is true that "generative grammar" is nearly universally accepted, and this comes from Chomsky. While the most popular current generative theory is transformational (Government and Binding theory), the role of transformations has been reduced radically, and much more emphasis is placed on interacting well formedness conditions on different levels of representations. Substantial minority theories, Generalized Phrase Structure Grammar, and Lexical Functional Grammar, do not employ transformations. A summary of these three theories can be found in "Lectures on Contemporary Syntactic Theories: An Introduction to government-Binding Theory, Generalized Phrase Structure Grammar, and Lexical-Functional Grammar" by Peter Sell. Published by the Center for the Study of Language and Information, and distributed by Chicago University Press. I have seen implementations based on LFG, GPSG (and an offshoot of that) as well as some other not transformational models. I have only once seen a GB based parser. It was very clever, but it only parsed four sentences. None of these theories were constructed with computer processing in mind, but it does turn out that it is often easier to build a parser based on nontransformation representations. None of the authors of these theories would claim that their theory was a better linguistic theory because of this property. >>> 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. I have seen parsers that build up semantic representations along with the syntax in which there is no sense that the syntax is prior. Again, I am directing follow-ups to my follow-up to sci.lang. -- Jeff Goldberg ARPA goldberg@russell.stanford.edu UUCP ...!ucbvax!russell.stanford.edu!goldberg
tfra@ur-tut.UUCP (Tom Frauenhofer) (06/01/87)
[Et tu, line-eater?] Actually, there is a (one-paragraph) discussion comparing BNF versus Transition Networks in the latest issue of AI Magazine (Volume 8, Number 1). It is part of the article "YANLI: A Powerful Natural Language Front-End Tool" by John C. Glasgow II. It even includes an example of a BNF and a Transition Network representation of the same grammar fragment.