Formative processes with applications to the decision problem in set theory I: powerset and singleton operators

  • Authors:
  • Domenico Cantone;Pietro Ursino

  • Affiliations:
  • Univ. di Catania, Catania, Italy;Univ. di Catania, Catania, Italy

  • Venue:
  • Information and Computation
  • Year:
  • 2002

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Abstract

This paper introduces formative processes, composed by transitivepartitions. Given a family F of sets, a formative processending in the Venn partition &egr; of F is shown toexist. Sufficient criteria are also singled out for a transitivepartition to model (via a function from set variables to unions ofsets in the partition) all set-literals modeled by &egr;. Onthe basis of such criteria a procedure is designed that mimics agiven formative process by another where sets have finite rankbounded by C (|&egr;|), with C a specificcomputable function. As a by-product, one of the core results ondecidability in computable set theory is rediscovered, namely theone that regards the satisfiability of unquantified set-theoreticformulae involving Boolean operators, the singleton-former, and thepowerset operator. The method described (which is able to exhibit aset-solution when the answer is affirmative) can be extended tosolve the satisfiability problem for broader fragments of settheory.