The complexity of quantified constraint satisfaction problems under structural restrictions

  • Authors:
  • Georg Gottlob;Gianluigi Greco;Francesco Scarcello

  • Affiliations:
  • Inst. für Informationssysteme, Technische Universität Wien, Vienna, Austria;Dip. di Matematica, Università della Calabria, Rende, Italy;DEIS, Università della Calabria, Rende, Italy

  • Venue:
  • IJCAI'05 Proceedings of the 19th international joint conference on Artificial intelligence
  • Year:
  • 2005

Quantified Score

Hi-index 0.00

Visualization

Abstract

We give a clear picture of the tractability/intractability frontier for quantified constraint satisfaction problems (QCSPs) under structural restrictions. On the negative side, we prove that checking QCSP satisfiability remains PSPACE-hard for all known structural properties more general than bounded treewidth and for the incomparable hypergraph acyclicity. Moreover, if the domain is not fixed, the problem is PSPACE-hard even for tree-shaped constraint scopes. On the positive side, we identify relevant tractable classes, including QCSPs with prefix Æ having bounded hypertree width, and QCSPs with a bounded number of guards. The latter are solvable in polynomial time without any bound on domains or quantifier alternations.