On three classes of automata-like P systems

  • Authors:

  • Rudolf Freund;Carlos Martín-Vide;Adam Obtułowicz;Gheorghe Paun

  • Affiliations:

  • Department of Computer Science, Technische Universität Wien, Wien, Austria;Research Group on Mathematical Linguistics, Rovira i Virgili University, Tarragona, Spain;Institute of Mathematics of the Polish Academy of Sciences, Warsaw, Poland;Research Group on Mathematical Linguistics, Rovira i Virgili University, Tarragona, Spain and Institute of Mathematics of the Romanian Academy, Bucuresti, Romania

  • Venue:
  • DLT'03 Proceedings of the 7th international conference on Developments in language theory
  • Year:
  • 2003

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Abstract

We investigate the three classes of accepting P systems considered so far, namely the P automata of Csuhaj-Varjú, Vaszil [3], their variant introduced by Madhu, Krithivasan [10], and the related machinery of Freund, Oswald [5]. All three variants of automata-like P systems are based on symport/antiport rules. For slight variants of the first two classes we prove that any recursively enumerable language can be recognized by systems with only two membranes (this considerably improves the result from [3], where systems with seven membranes were proved to be universal). We also introduce the initial mode of accepting strings (the strings are introduced into the system, symbol by symbol, at the beginning of a computation), and we briefly investigate this mode for the three classes of automata, especially for languages over a one-letter alphabet. Some open problems are formulated, too.