Topic
Chomsky hierarchy
About: Chomsky hierarchy is a research topic. Over the lifetime, 601 publications have been published within this topic receiving 31067 citations. The topic is also known as: Chomsky–Schützenberger hierarchy.
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01 Jan 1974
TL;DR: Language as an instrument of communication and carrier of information is a psychophysical entity, because the performance of a language is surely as much dependent on its physical environment as on the mental nuances of its users.
Abstract: Language as an instrument of communication and carrier of information is a very complex phenomenon. It is a psychophysical entity, because the performance of a language is surely as much dependent on its physical environment as on the mental nuances of its users. Historical factors, emotions, and all other elements which constitute the complex structure and workings of the human mind and human institutions have significant roles in the usage and development of languages.
8 citations
8 citations
02 Jan 1991
TL;DR: In this article, the fundamental notions about formal power series and languages are discussed, and Markov algorithms are compared to grammars and Post canonical systems, a class of generating devices that are somewhat different from grammar, but still equivalent to grammar in the sense that the family of languages generated by the new devices equals the families of recursively enumerable languages.
Abstract: Publisher Summary This chapter discusses formal language theory and focuses on a specific tool called formal power series. Formal language theory, together with automata theory, is the oldest branch of theoretical computer science. The chapter discusses the fundamental notions about formal power series and languages. It also various normal forms for grammars. The chapter describes a class of generating devices that are somewhat different from grammars but still equivalent to grammars in the sense that the family of languages generated by the new devices equals the family of recursively enumerable languages. The new devices, called Post canonical systems or Post systems, very closely resemble formal systems in logic. The productions have the shape of inference rules. The family of languages generated by Post systems equals the family of recursively enumerable languages. The chapter discusses Markov algorithms, which resemble the intuitive notion of an algorithm. Viewed as language-defining devices, Markov algorithms are equivalent to grammars and Post systems.
8 citations
TL;DR: It is proved the existence of linear languages which are not δ -similar to any regular language for any δ < ½ and for δ ≥ ½ this is unknown but it could only be possible in the case of non-slender linear languages.
Abstract: Punctured languages are languages whose words are partial words in the sense that the letters at some positions are unknown We investigate to which extent restoration of punctured languages is possible if the number of unknown positions or the proportion of unknown positions per word, respectively, is bounded, and we study their relationships for different boundings The considered restoration classes coincide with similarity classes according to some kind of similarity for languages Thus all results we can also formulate in the language of similarity We show some hierarchies of similarity classes for each class from the Chomsky hierarchy and prove the existence of linear languages which are not δ -similar to any regular language for any δ < ½ For δ ≥ ½ this is unknown but it could only be possible in the case of non-slender linear languages (© 2006 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim)
8 citations