Showing papers on "Indexed language published in 1973"
TL;DR: The present purpose is to foster studies which model grammatical transformations as mappings on trees (equivalently, labeled bracketings) and investigating questions of current linguistic interest, such as the recursiveness of languages generated by transformational grammars.
186 citations
TL;DR: The uvwxy-theorem of context-free languages is extended and it is shown that the finiteness problem for the indexed languages is solvable and certain languages such as {anl
^l} and {($ w)lwl |w;e {a, &}*} are not indexed languages.
Abstract: In this paper, the uvwxy-theorem of context-free languages is extended to the case of indexed languages. Applying the extended theorem, it is shown that the finiteness problem for the indexed languages is solvable and certain languages such as {anl
^l} and {($ w)lwl |w;e {a, &}*} are not indexed languages.
72 citations
TL;DR: An infinite hierarchy of classes of languages is exhibited between the class of context-sensitive languages and the classof context-free languages.
Abstract: The class of languages expressible as the intersection ofk context-free languages is shown to be properly contained within the class of languages expressible as the intersection ofk + 1 context-free languages. Hence an infinite hierarchy of classes of languages is exhibited between the class of context-sensitive languages and the class of context-free languages.
63 citations
15 Oct 1973
TL;DR: A class of naturallanguage grammars is formalized and the sentence-recognition problem is shown to be polynomial-hard although the languages are context-sensitive, and new language-theoretic characterizations are given.
Abstract: Complexity of sentence recognition is studied for one-way stack languages, indexed languages, and tree transducer languages The problem is shown to be polynomial-complete in each case A class of naturallanguage grammars is formalized and the sentence-recognition problem is shown to be polynomial-hard although the languages are context-sensitive The proofs give new language-theoretic characterizations of the set of satisfiable propositional formulas and the set of prepositional tautologies
56 citations
TL;DR: Some specific aspects of language structure are examined in detail in the context of pattern analysis, and the characteristics of the transformational grammars of linguists show up even in this simple example.
14 citations
TL;DR: An extension for the concept of the finite index of context-free grammars is introduced and regular control languages are derived for the resulting family of languages generated by ordered Context-free Grammars.
Abstract: An extension for the concept of the finite index of context-free grammars is introduced and regular control languages are derived for the resulting family of languages generated by ordered context-free grammars.
2 citations