Abstract
The study of various decision problems for logic fragments has a long history in computer science. This paper is on the membership problem for a fragment of first-order logic over infinite words; the membership problem asks for a given language whether it is definable in some fixed fragment. The alphabetic topology was introduced as part of an effective characterization of the fragment Σ2 over infinite words. Here, Σ2 consists of the first-order formulas with two blocks of quantifiers, starting with an existential quantifier. Its Boolean closure is \(\mathbb {B}{\Sigma }_{2}\). Our first main result is an effective characterization of the Boolean closure of the alphabetic topology, that is, given an ω-regular language L, it is decidable whether L is a Boolean combination of open sets in the alphabetic topology. This is then used for transferring Place and Zeitoun’s recent decidability result for \(\mathbb {B}{\Sigma }_{2}\) from finite to infinite words.
Similar content being viewed by others
Notes
During the preparation of this submission, we learned that Pierron, Place and Zeitoun [10] independently found another proof for the decidability of \(\mathbb {B}{\Sigma }_{2}\) over infinite words. For documenting the independency of the two proofs, we also include the technical report [7] of this paper in the list of references.
References
Brzozowski, J.A., Knast, R.: The dot-depth hierarchy of star-free languages is infinite. J. Comput. Syst. Sci. 16(1), 37–55 (1978)
Diekert, V., Gastin, P., Kufleitner, M.: A survey on small fragments of first-order logic over finite words. Int. J. Found Comput. Sci. 19(3), 513–548 (2008)
Diekert, V., Kufleitner, M.: Fragments of first-order logic over infinite words. Theory Comput. Syst. 48(3), 486–516 (2011)
Eilenberg, S.: Automata Languages, and Machines, volume B. Academic Press (1976)
Kallas, J., Kufleitner, M., Lauser, A.: First-order fragments with successor over infinite words. In: STACS 2011, Proceedings, Volume 9 of LIPIcs, pp 356–367. Dagstuhl Publishing (2011)
Kozen, D.: Lower bounds for natural proof systems. In: Proceedings of the 18th Annual Symposium on Foundations of Computer Science, FOCS’77, pp 254–266. IEEE Computer Society Press, Providence, Rhode Island (1977)
Kufleitner, M., Walter, T.: Level two of the quantifier alternation hierarchy over infinite words. arXiv:1509.06207 (2015)
Kufleitner, M., Walter, T.: One quantifier alternation in first-order logic with modular predicates. RAIRO-Theor. Inf. Appl. 49(1), 1–22 (2015)
Perrin, D., Pin, J.: Infinite Words, volume 141 of Pure and Applied Mathematics. Elsevier (2004)
Pierron, T., Place, T., Zeitoun, M.: Quantifier alternation for infinite words. arXiv:1511.09011 (2015)
Pin, J.: A variety theorem without complementation. In: Russian Mathematics (Iz. VUZ), vol. 39, pp 80–90 (1995)
Pin, J.: Syntactic semigroups. In: Handbook of Formal Languages, vol. 1, pp 679–746. Springer (1997)
Place, T., Zeitoun, M.: Going higher in the first-order quantifier alternation hierarchy on words. In: ICALP 2014, Proceedings, Part II, vol. 8573 of LNCS, pp 342–353. Springer (2014)
Ramsey, F.P.: On a problem of formal logic. Proc. London Math. Soc. 30, 264–286 (1930)
Schwarz, S., Staiger, L.: Topologies Refining the Cantor Topology on X ω. In: IFIP TCS 2010, Proceedings, Volume 323 of 1 Advances in Information and Communication Technology, pp 271–285. Springer (2010)
Staiger, L., Wagner, K.W.: Automatentheoretische und automatenfreie Charakterisierungen topologischer Klassen Regulärer Folgenmengen. Elektron. Inform.-verarb Kybernetik 10, 379–392 (1974)
Straubing, H.: Finite semigroup varieties of the form \(\mathbb {V}\mathbb {D}\). J Pure Appl. Algebra 36(1), 53–94 (1985)
Straubing, H.: Finite Automata, Formal Logic, and Circuit Complexity. Birkhäuser (1994)
Thomas, W.: Classifying regular events in symbolic logic. J. Comput. Syst. Sci. 25, 360–376 (1982)
Thomas, W.: Automata on infinite objects. In: Handbook of Theoretical Computer Science, Chapter 4, pp 133–191. Elsevier (1990)
Wilke, T.: Locally Threshold Testable Languages of Infinite Words. In: STACS ’93, Proceedings, Volume 665 of LNCS, pp 607–616. Springer (1993)
Author information
Authors and Affiliations
Corresponding author
Additional information
This work was supported by the German Research Foundation (DFG) under grants DI 435/5-2 and DI 435/6-1.
Rights and permissions
About this article
Cite this article
Kufleitner, M., Walter, T. Level Two of the Quantifier Alternation Hierarchy Over Infinite Words. Theory Comput Syst 62, 467–480 (2018). https://doi.org/10.1007/s00224-017-9801-x
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00224-017-9801-x