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The Hardest Language for Conjunctive Grammars

  • Alexander OkhotinEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 9691)

Abstract

A famous theorem by Greibach (“The hardest context-free language”, SIAM J. Comp., 1973) states that there exists such a context-free language \(L_0\) that every context-free language over any alphabet is reducible to \(L_0\) by a homomorphic reduction—in other words, is representable as an inverse homomorphic image \(h^{-1}(L_0)\), for a suitable homomorphism h. This paper establishes similar characterizations for conjunctive grammars, that is, for grammars extended with a conjunction operator.

Keywords

Normal Form Parse Tree Membership Problem Nonterminal Symbol Language Equation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Department of Mathematics and StatisticsUniversity of TurkuTurkuFinland

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