Weak alternating automata and tree automata emptiness

Orna Kupferman*, Moshe Y. Vardi

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

84 Scopus citations


Automata on infinite words and trees are used for specification and verification of nonterminating programs. The verification and the satisfiability problems of specifications can be reduced to the nonemptiness problem of such automata. In a weak automaton, the state space is partitioned into partially ordered sets, and the automaton can proceed from a certain set only to smaller sets. Reasoning about weak automata is easier than reasoning about automata with no restricted structure. In particular, the nonemptiness problem for weak alternating automata over a singleton alphabet can be solved in linear time. Known translations of alternating automata to weak alternating automata involve determinization, and therefore involve a double exponential blow-up. In this paper we describe simple and efficient translations, which circumvent the need for determinization, of parity and Rabin alternating word automata to weak alternating word automata. Beyond the independent interest of such translations, they give rise to a simple algorithm for deciding the nonemptiness of nondeterministic parity and Rabin tree automata. In particular, our algorithm for Rabin automata runs in time O(n2k+1·k!), where n is the number of states in the automaton and k is the number of pairs in the acceptance condition. This improves the known O((nk)3k) bound for the problem.

Original languageAmerican English
Pages (from-to)224-233
Number of pages10
JournalConference Proceedings of the Annual ACM Symposium on Theory of Computing
StatePublished - 1998
Externally publishedYes
EventProceedings of the 1998 30th Annual ACM Symposium on Theory of Computing - Dallas, TX, USA
Duration: 23 May 199826 May 1998


Dive into the research topics of 'Weak alternating automata and tree automata emptiness'. Together they form a unique fingerprint.

Cite this