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A parallel context-free derivation hierarchy

  • Klaus Reinhardt
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1684)

Abstract

We consider the number of parallel derivation steps as complexity measure for context-free languages and show that a strict and dense hierarchy is obtained between logarithmic and linear (arbitrary) tree height. We hereby improve a result of Gabarro. Furthermore we give a non-regular language with logarithmic tree height disproving a conjecture of Culik and Maurer. As a new method we use counter-representations, where the successor relation can be handled as the complement of context-free languages.

Keywords

Tree Height Turing Machine Regular Language Derivation Tree Pushdown Automaton 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Klaus Reinhardt
    • 1
  1. 1.Wilhelm-Schickhard Institut für InformatikUniversität TübingenTübingenGermany

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