Visibly Pushdown Transducers with Look-Ahead

  • Emmanuel Filiot
  • Frédéric Servais
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7147)


Visibly Pushdown Transducers (VPT) form a subclass of pushdown transducers. In this paper, we investigate the extension of VPT with visibly pushdown look-ahead (VPT la ). Their transitions are guarded by visibly pushdown automata that can check whether the well-nested subword starting at the current position belongs to the language they define. First, we show that VPT la are not more expressive than VPT, but are exponentially more succinct. Second, we show that the class of deterministic VPT la corresponds exactly to the class of functional VPT, yielding a simple characterization of functional VPT. Finally, we show that while VPT la are exponentially more succinct than VPT, checking equivalence of functional VPT la is, as for VPT, ExpT-C. As a consequence, we show that any functional VPT is equivalent to an unambiguous one.


Tree Automaton Input Word Tree Transducer Call Transition Return Transition 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Emmanuel Filiot
    • 1
  • Frédéric Servais
    • 2
    • 3
  1. 1.Université Libre de BruxellesBelgium
  2. 2.Hasselt UniversityBelgium
  3. 3.Transnational University of LimburgBelgium

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