The finite graph problem for two-way alternating automata

The Finite Graph Problem for Two-Way Alternating Automata

Two-way alternating automata on trees were introduced by Vardi [Va98]. Here we consider alternating two-way automata on graphs and show the decidability of the following problem: ,,does a given automaton with the Büchi condition accept any finite graph?” Using this result we demonstrate the decidability of the finite model problem for a certain fragment of the modal μ-calculus with backward mod...

Alternating two-way AC-tree automata

We explore the notion of alternating two-way tree automata modulo the theory of finitely many associative-commutative (AC) symbols. This was prompted by questions arising in cryptographic protocol verification, in particular in modeling group key agreement schemes based on Diffie-Hellman-like functions, where the emptiness question for intersections of such automata is fundamental. This also ha...

Complementing Two-Way Finite Automata

We study the relationship between the sizes of two-way finite automata accepting a language and its complement. In the deterministic case, for a given automaton (2dfa) with n states, we build an automaton accepting the complement with at most 4n states, independently of the size of the input alphabet. Actually, we show a stronger result, by presenting an equivalent 4n-state 2dfa that always hal...

Determinizing Two-way Alternating Pebble Automata for Data Languages

We prove that for every integer k ≥ 1, two-way alternating kpebble automata and one-way deterministic k-pebble automata for data languages have the same recognition power.

The Finite Graph Problem for Two - WayAlternating