Showing papers on "Chomsky hierarchy published in 1969"

An Infinite Hierarchy of Context-Free Languages

Abstract: By generalizing the notions of a one counter machine and of a finite turn pushdown store automaton, it is possible to define an omega 2-hierarchy of families of context-free languages such that each subfamily is infinite, closed under union, concatenation and closure, homomorphism, intersection with regular sets and inverse homomorphism and reversal. Each subfamily can be characterized in a manner akin to the Chomsky-Schutzenberger characterization of the context-free languages. Whenever two subfamilies are incomparable it is undecidable whether a member of one belongs to the other.

String adjunct grammars

Abstract: In this paper, we have introduced a new style of formal grammars called String Adjunct Grammars (AG) The rules in an AG have a considerably different formal character as compared to the 'rewrite rule' in a Phrase Structure Grammar (PSG) Such a study of formal grammars of different styles (ie, formal character of rules) is of great interest because each style is well suited for characterizing certain aspects of natural language structure and is awkward for characterizing certain other aspects Several subclasses of AG's motivated by strong linguistic considerations have been studied, comparing them with PSG's Linguistic relevance of these grammars (and other gram mars suggested by this study) has been discussed at the end

Operators and Nucleus: A Contribution to the Theory of Grammar

Abstract: 1. Preliminaries 2. Chomsky's model of grammatical description 3. Criticisms of Chomsky's model 4. Deep structure and operators 5. A specimen of description Bibliography Index.

Properties of formal grammars with mixed types of rules and their linguistic relevance

Abstract: In this paper, we will study a class of formal grammars with mixed types of rules. The reason for considering such grammars is that no single style (i.e., formal character of rules) of formal grammars is able to represent the various aspects of language structure in a natural way. Various considerations for setting up such grammars have been discussed. Generation schemes which map strings in the language of one mixed grammar into strings in the language of another mixed grammar (both strings being 'well-formed') have been studied. Linguistic relevance of these concepts has also been discussed.