Understanding planning with incomplete information and sensing

  • Authors:
  • Marcelo Oglietti

  • Affiliations:
  • Universitá di Roma "La Sapienza", Dipartimento di Informatica e Sistemistica, Via Salaria 113, 00198 Rome, Italy and CONAE-Argentine National Space Agency, Paseo Colon 751, C1063ACH Buenos Ai ...

  • Venue:
  • Artificial Intelligence
  • Year:
  • 2005

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Abstract

PKS is the framework for planning with incomplete information and sensing recently introduced by Bacchus and Petrick [Proc. KR'98, pp. 432-443]. The fact that PKS generalizes STRIPS to domains with incomplete information and sensing opens up the possibility of proposing it as a reference for comparisons with other formalisms that approach the problem from different perspectives.To this end we first provide a formal semantics for PKS, then analyze and extend it. The formal definition of the extended PKS entails the identification of a number of properties of this planning framework. In particular, we prove that for any finite instance of the PKS planning problem the reachable states are finite; on the basis of this result we propose an improved planning algorithm that is not only sound, as the one proposed by Petrick and Bacchus [Proc. AIPS'02, pp. 212-221], but also complete.We extend PKS to include conditional plans with cycles and introduce the distinction between different classes of solutions: strong, strong cyclic, weak acyclic and weak cyclic. In contrast with current belief, we prove that some weak acyclic solutions are more likely to succeed for a limited execution than some strong cyclic solutions, revealing the lack of a method for judging the quality of different solutions. Finally, we introduce a quality measure for solutions of any class, and a quantitative method for comparing them.