Alternating Automata and a Temporal Fixpoint Calculus for Visibly Pushdown Languages
- Cite this paper as:
- Bozzelli L. (2007) Alternating Automata and a Temporal Fixpoint Calculus for Visibly Pushdown Languages. In: Caires L., Vasconcelos V.T. (eds) CONCUR 2007 – Concurrency Theory. CONCUR 2007. Lecture Notes in Computer Science, vol 4703. Springer, Berlin, Heidelberg
We investigate various classes of alternating automata for visibly pushdown languages (VPL) over infinite words. First, we show that alternating visibly pushdown automata (AVPA) are exactly as expressive as their nondeterministic counterpart (NVPA) but basic decision problems for AVPA are 2Exptime-complete. Due to this high complexity, we introduce a new class of alternating automata called alternating jump automata (AJA). AJA extend classical alternating finite-state automata over infinite words by also allowing non-local moves. A non-local forward move leads a copy of the automaton from a call input position to the matching-return position. We also allow local and non-local backward moves. We show that one-way AJA and two-way AJA have the same expressiveness and capture exactly the class of VPL. Moreover, boolean operations for AJA are easy and basic decision problems such as emptiness, universality, and pushdown model-checking for parity two-way AJA are Exptime-complete. Finally, we consider a linear-time fixpoint calculus which subsumes the full linear-time μ-calculus (with both forward and backward modalities) and the logic CaRet and captures exactly the class of VPL. We show that formulas of this logic can be linearly translated into parity two-way AJA, and vice versa. As a consequence satisfiability and pushdown model checking for this logic are Exptime-complete.
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