0-1 Laws for Fragments of Existential Second-Order Logic: A Survey

  • Authors:
  • Phokion G. Kolaitis;Moshe Y. Vardi

  • Affiliations:
  • -;-

  • Venue:
  • MFCS '00 Proceedings of the 25th International Symposium on Mathematical Foundations of Computer Science
  • Year:
  • 2000

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Abstract

The probability of a property on the collection of all finite relational structures is the limit as n → ∞ of the fraction of structures with n elements satisfying the property, provided the limit exists. It is known that the 0-1 law holds for every property expressible in first-order logic, i.e., the probability of every such property exists and is either 0 or 1. Moreover, the associated decision problem for the probabilities is solvable. In this survey, we consider fragments of existential second-order logic in which we restrict the patterns of first-order quantifiers. We focus on fragments in which the first-order part belongs to a prefix class. We show that the classifications of prefix classes of first-order logic with equality according to the solvability of the finite satisfiability problem and according to the 0-1 law for the corresponding +11 fragments are identical, but the classifications are different without equality.