A Playful Glance at Hierarchical Questions for Two-Way Alternating Automata

Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 5489)


Two-way alternating automata were introduced by Vardi in order to study the satisfiability problem for the modal μ-calculus extended with backwards modalities. In this paper, we present a very simple proof by way of Wadge games of the strictness of the hierarchy of Motowski indices of two-way alternating automata over trees.


Binary Tree Terminal Node Hierarchy Problem Winning Strategy Game Language 
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© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  1. 1.Faculté des Hautes Études Commerciales, Institut des Systèmes d’informationUniversité de LausanneLausanneSwitzerland
  2. 2.Laboratoire Bordelais de Recherche en InformatiqueUniversité Bordeaux 1Talence cedexFrance

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