Existential Second-Order Logic Over Strings

  • Thomas Eiter ,
  • Georg Gottlob ,
  • Yuri Gurevich

Journal of the ACM, | , Vol 47(1): pp. 77-131

We study existential second-order logic over finite strings. For every prefix class C, we determine the complexity of the model checking problem restricted to C. In particular, we prove that, in the case of the Ackermann class, for every formula φ, there is a finite automaton A that solves the model checking problem for φ.