Acta Informatica

, Volume 26, Issue 3, pp 279–284 | Cite as

The method of forced enumeration for nondeterministic automata

  • Róbert Szelepcsényi


Every family of languages, recognized by nondeterministic L(n) tape-bounded Turing machines, where L(n)≥logn, is closed under complement. As a special case, the family of context-sensitive languages is closed under complement. This solves the open problem from [4].


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Hopcroft, J.E., Ullman, J.D.: Formal languages and their relation to automata. Reading: Addison-Wesley 1969Google Scholar
  2. 2.
    Immerman, N.: Nondeterministic space is closed under complementation. Proceedings of the 3rd Annual Conference Structure in Complexity Theory, 14–17 June 1988, Washington D.C. (also TH Report YALEU/DCS/TR 552, July 1987)Google Scholar
  3. 3.
    Immerman, N.: Descriptive and computational complexity, (unpublished manuscript, 1987)Google Scholar
  4. 4.
    Kuroda, S.Y.: Classes of languages and linear-bounded automata. Inf. Control 7, 207–233 (1964)Google Scholar
  5. 5.
    Szelepcsényi, R.: Context-sensitive languages are closed under complementation, TR Komensky University, April 1987 (in Slovak)Google Scholar
  6. 6.
    Szelepcsényi, R.: The method of Forcing for nondeterministic automata. Bull. Eur. Assoc. Theor. Comp. Sci. 33, 96–100 (1987)Google Scholar

Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Róbert Szelepcsényi
    • 1
  1. 1.Department of Theoretical Cybernetics, Faculty of Mathematics and PhysicsKomensky UniversityBratislavaCzechoslovakia

Personalised recommendations