The complexity of enriched µ-calculi

  • Authors:
  • Piero A. Bonatti;Carsten Lutz;Aniello Murano;Moshe Y. Vardi

  • Affiliations:
  • Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Napoli, Italy;TU Dresden, Institute for Theoretical Computer Science, Dresden, Germany;Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Napoli, Italy;Dept. of Computer Science, Microsoft Research and Rice University, TX

  • Venue:
  • ICALP'06 Proceedings of the 33rd international conference on Automata, Languages and Programming - Volume Part II
  • Year:
  • 2006

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Abstract

The fully enriched μ-calculus is the extension of the propositional μ-calculus with inverse programs, graded modalities, and nominals. While satisfiability in several expressive fragments of the fully enriched μ-calculus is known to be decidable and ExpTime-complete, it has recently been proved that the full calculus is undecidable. In this paper, we study the fragments of the fully enriched μ-calculus that are obtained by dropping at least one of the additional constructs. We show that, in all fragments obtained in this way, satisfiability is decidable and ExpTime-complete. Thus, we identify a family of decidable logics that are maximal (and incomparable) in expressive power. Our results are obtained by introducing two new automata models, showing that their emptiness problems are ExpTime-complete, and then reducing satisfiability in the relevant logics to this problem. The automata models we introduce are two-way graded alternating parity automata over infinite trees (2GAPT) and fully enriched automata (FEA) over infinite forests. The former are a common generalization of two incomparable automata models from the literature. The latter extend alternating automata in a similar way as the fully enriched μ-calculus extends the standard μ-calculus