Combination of disjoint theories: beyond decidability

  • Authors:
  • Pascal Fontaine;Stephan Merz;Christoph Weidenbach

  • Affiliations:
  • Université de Lorraine & LORIA, Nancy, France;INRIA Nancy & LORIA, Nancy, France;Max-Planck-Institut für Informatik, Saarbrücken, Germany

  • Venue:
  • IJCAR'12 Proceedings of the 6th international joint conference on Automated Reasoning
  • Year:
  • 2012

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Abstract

Combination of theories underlies the design of satisfiability modulo theories (SMT) solvers. The Nelson-Oppen framework can be used to build a decision procedure for the combination of two disjoint decidable stably infinite theories. We here study combinations involving an arbitrary first-order theory. Decidability is lost, but refutational completeness is preserved. We consider two cases and provide complete (semi-)algorithms for them. First, we show that it is possible under minor technical conditions to combine a decidable (not necessarily stably infinite) theory and a disjoint finitely axiomatized theory, obtaining a refutationally complete procedure. Second, we provide a refutationally complete procedure for the union of two disjoint finitely axiomatized theories, that uses the assumed procedures for the underlying theories without modifying them.