Fuzzy Description Logic Reasoning Using a Fixpoint Algorithm

  • Authors:

  • Uwe Keller;Stijn Heymans

  • Affiliations:

  • Semantic Technology Institute (STI) Innsbruck, University of Innsbruck, Austria;Knowledge-based Systems Group, Institute of Information Systems, Vienna University of Technology, Austria

  • Venue:
  • LFCS '09 Proceedings of the 2009 International Symposium on Logical Foundations of Computer Science
  • Year:
  • 2009

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Abstract

We present ${\mathbf{FixIt}}{\mathbb{(ALC)}}$, a novel procedure for deciding knowledge base (KB) satisfiability in the Fuzzy Description Logic (FDL) ${\mathbb{ALC}}$. ${\mathbf{FixIt}}{\mathbb{(ALC)}}$ does not search for tree-structured models as in tableau-based proof procedures, but embodies a (greatest) fixpoint-computation of canonical models that are not necessarily tree-structured, based on a type-elimination process. Soundness, completeness and termination are proven and the runtime and space complexity are discussed. We give a precise characterization of the worst-case complexity of deciding KB satisfiability (as well as related terminological and assertional reasoning tasks) in ${\mathbb{ALC}}$ in the general case and show that our method yields a worst-case optimal decision procedure (under reasonable assumptions). To the best of our knowledge it is the first fixpoint-based decision procedure for FDLs, hence introducing a new class of inference procedures into FDL reasoning.