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Showing papers on "Chomsky hierarchy published in 1985"


Journal ArticleDOI
TL;DR: In searching for universal constraints on the class of natural languages, linguists have investigated a number of formal properties, including that of context-freeness, which is interpreted strongly and weakly both as a way of characterizing structure sets and even weakly for characterizing string sets.
Abstract: In searching for universal constraints on the class of natural languages, linguists have investigated a number of formal properties, including that of context-freeness. Soon after Chomsky’s categorization of languages into his well-known hierarchy (Chomsky, 1963), the common conception of the context-free class of languages as a tool for describing natural languages was that it was too restrictive a class — interpreted strongly (as a way of characterizing structure sets) and even weakly (as a way of characterizing string sets).

638 citations


Book ChapterDOI
TL;DR: What is currently known about natural language morphology and syntax from the perspective of formal language theory is surveyed and recent developments such as feature-theory, the use of extension and unification, default mechanisms, and metagram-matical techniques are outlined.
Abstract: This paper surveys what is currently known about natural language morphology and syntax from the perspective of formal language theory. Firstly, the position of natural language word-sets and sentence-sets on the formal language hierarchy is discussed. Secondly, the contemporary use by linguists of a range of formal grammars (from finite state transducers to indexed grammars) in both word-syntax (i.e. morphology) and sentence-syntax is sketched. Finally, recent developments such as feature-theory, the use of extension and unification, default mechanisms, and metagram-matical techniques, are outlined.

55 citations



Proceedings ArticleDOI
27 Mar 1985
TL;DR: The central claim of the paper is that NL stringsets are regular: three independent arguments are offered in favor of this position: one based on parsimony considerations, one employing the McCullogh-Pitts (1943) model of neuruns, and a purely linguistic one.
Abstract: The central claim of the paper is that NL stringsets are regular. Three independent arguments are offered in favor of this position: one based on parsimony considerations, one employing the McCullogh-Pitts (1943) model of neuruns, and a purely linguistic one. It is possible to derive explicit upper bounds for the number of (live) states in NL acceptors: the results show that finite state NL parsers can be implemented on present-day computers. The position of NL stringsets within the regular family is also investigated: it is proved that NLs are counter-free, but not locally testable.

14 citations


Proceedings Article
Glenn D. Blank1
18 Aug 1985
TL;DR: Register Vector Grammar is a new kind of f in i te -s ta te automaton that is sensitive to context—without, of course, being contextsensitive in the sense of Chomsky hierarchy.
Abstract: Register Vector Grammar is a new kind of f in i te -s ta te automaton that is sensitive to context—without, of course, being contextsensitive in the sense of Chomsky hierarchy Traditional automata are functionally simple: symbols match by identi ty and change by replacement RVG is functionally complex: ternary feature vectors (eg +-±--++) match and change by masking ( + matches but does not change any value) Functional complexity—as opposed to the computat ional complexity of non-finite memory—is well suited for modelling multiple and discontinuous constraints RVG is thus very good at handling the permutations and dependencies of syntax (wh-questions are explored as example) Because center-embedding in natural languages is in fact very shallow and constrained, context-free power is not needed RVG can thus be guaranteed to run in a small l inear time, because it is FS, and yet can capture generalizations and constraints that functionally simple FS grammars cannot

4 citations


Journal ArticleDOI
TL;DR: In this article, two classes of generalized semi-Thue systems are introduced and two infinite hierarchies of languages are obtained in this way, and the capacity of these generative mechanisms and the closure properties of the obtained families of languages were investigated.
Abstract: In this paper, two classes of generalized semi-Thue systems are introduced. Two infinite hierarchies of languages are obtained in this way. The capacity of these generative mechanisms and the closure properties of the obtained families of languages are investigated.