A note on partially ordered tree automata

  • Authors:
  • P. -C. Héam

  • Affiliations:
  • Laboratoire d'Informatique de l'Université de Franche-Comté, 16 route de Gray, 25030 Besançon Cedex, France

  • Venue:
  • Information Processing Letters
  • Year:
  • 2008

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Abstract

A recent paper by Bouajjani, Muscholl and Touili shows that the class of languages accepted by partially ordered word automata (or equivalently accepted by @S"2-formulae) is closed under semi-commutation and it suggested the following open question: can we extend this result to tree languages? This problem can be addressed by proving (1) that the class of tree regular languages accepted by @S"2 formulae is strictly included in the class of languages accepted by partially ordered automata, and (2) that Bouajjani and the others results cannot be extended to tree.