Some contributions to the metatheory of the situation calculus

  • Authors:

  • Fiora Pirri;Ray Reiter

  • Affiliations:

  • Univ. delgi Studi di Roma “La Sapienza” via Salaria 113, Rome, Italy;Univ. of Toronto, Toronto, Ont., Canada

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1999

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Abstract

We focus on a rich axiomatization for actions in the situation calculus that includes, among other features, a solution to the frame problem for deterministic actions. Our work is foundational in nature, directed at simplifying the entailment problem for these axioms. Specifically, we make four contributions to the metatheory of situation calculus axiomatizations of dynamical systems: (1) We prove that the above-mentioned axiomatization for actions has a relative satisfiability property; the full axiomatization is satisfiable iff the axioms for the initial state are. (2)We define the concept of regression relative to these axioms, and prove a soundness and completeness theorem for a regression-based approach to the entailment problem for a wide class of queries. (3) Our formalization of the situation calculus requires certain foundational axioms specifying the domain of situations. These include an induction axiom, whose presence complicates human and automated reasoning in the situation calculus. We characterize various classes of sentences whose proofs do not require induction, and in some cases, some of the other foundational axioms. (4)We prove that the logic programming language GOLOG never requires any of the foundational axioms for the evaluation of programs.