Weak Büchi automaton

In computer science and automata theory, a Weak Büchi automaton is a formalism which represents a set of infinite words. A Weak Büchi automaton is a modification of Büchi automaton such that for all pair of states $q$ and $q'$ belonging to the same strongly connected component, $q$ is accepting if and only if $q'$ is accepting.

A Büchi automaton accepts a word $w$ if there exists a run, such that at least one state occurring infinitely often in the final state set $F$ . For Weak Büchi automata, this condition is equivalent to the existence of a run which ultimately stays in the set of accepting states.

Weak Büchi automata are strictly less-expressive than Büchi automata and than Co-Büchi automata.

Properties edit

The deterministic Weak Büchi automata can be minimized in time $O(n\log(n))$ .^[1]

The languages accepted by Weak Büchi automata are closed under union and intersection but not under complementation. For example, $(a+b)^{*}b^{\omega }$ can be recognised by a Weak Büchi automaton but its complement $(b^{*}a)^{\omega }$ cannot.

Non-deterministic Weak Büchi automata are more expressive than Weak Büchi automata. As an example, the language $(a+b)^{*}b^{\omega }$ can be decided by a Weak Büchi automaton but by no deterministic Büchi automaton.

References edit

^ Löding, Christof (2001). "Efficient Minimization of Deterministic Weak ω-Automata". Information Processing Letters. 79 (3): 105–109. doi:10.1016/S0020-0190(00)00183-6.

Boigelot, Bernard (3 July 2005). "An effective decision procedure for linear arithmetic over the integers and reals" (PDF). ACM Transactions on Computational Logic. 6 (3): 614–633. doi:10.1145/1071596.1071601.

[1] Löding, Christof (2001). "Efficient Minimization of Deterministic Weak ω-Automata". Information Processing Letters. 79 (3): 105–109. doi:10.1016/S0020-0190(00)00183-6.

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