Topic
Indexed language
About: Indexed language is a research topic. Over the lifetime, 334 publications have been published within this topic receiving 11000 citations.
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08 Aug 2013TL;DR: This work proposes an extension of the class of languages captured by these formalisms that is arguably mildly context-sensitive, based on a mild use of a copying operation the authors call IO-substitution.
Abstract: The class of mildly context-sensitive languages is commonly regarded as sufficiently rich to capture most aspects of the syntax of natural languages. Many formalisms are known to generate families of languages which belong to this class. Among them are tree-adjoining grammars, multiple context-free grammars and abstract categorial grammars. All these formalisms have in common that they are based on operations which do not copy already derived material in the course of a derivation. We propose an extension of the class of languages captured by these formalisms that is arguably mildly context-sensitive. This extension is based on a mild use of a copying operation we call IO-substitution.
10 citations
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23 May 2011TL;DR: This work refines the relationship among the classes of languages generated by the above grammars and Local languages and states some considerations about closure properties of (regular) pure 2D context-free languages.
Abstract: Many formal models have been proposed to recognize or to generate two-dimensional words. In this paper, we focus our analysis on (regular) pure 2D context-free grammars, regional tile grammars and Průsa grammars, showing that nevertheless they have been proposed as a generalization of string context free grammars their expressiveness is different. This work refines the relationship among the classes of languages generated by the above grammars and Local languages and states some considerations about closure properties of (regular) pure 2D context-free languages.
10 citations
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TL;DR: This paper studies the representation of the derivations in phrase-structure grammars by the use of “derivation languages,” where the words in the derivation language of a grammar correspond exactly to the “syntactical graphs” of Loeckx (1970).
Abstract: This paper studies the representation of the derivations in phrase-structure grammars by the use of “derivation languages.” The words in the derivation language of a grammar correspond exactly to the “syntactical graphs” of Loeckx (1970) . Furthermore, the derivation languages generalize the representation of context-free derivation trees in prefix form. “Graph automata” are developed as acceptors of the derivation languages. The graph automata generalize the theory of tree automata as studied in connection with contextfree grammars.
10 citations
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22 Jun 1993TL;DR: It will be shown that using variables in lexical categories can increase the weak generative capacity of CCGs beyond the class of grammars listed above.
Abstract: Combinatory Categorial Grammars, CCGs, (Steedman 1985) have been shown by Weir and Joshi (1988) to generate the same class of languages as Tree-Adjoining Grammars (TAG), Head Grammars (HG), and Linear Indexed Grammars (LIG). In this paper, I will discuss the effect of using variables in lexical category assignments in CCGs. It will be shown that using variables in lexical categories can increase the weak generative capacity of CCGs beyond the class of grammars listed above.
10 citations