Unification in Description Logics has been proposed as a novel inference service that can, for example, be used to detect redundancies in ontologies. In a recent paper, we have shown that unification in \(\mathcal{EL}\) is NP-complete, and thus of a complexity that is considerably lower than in other Description Logics of comparably restricted expressive power. In this paper, we introduce a new NP-algorithm for solving unification problems in \(\mathcal{EL}\), which is based on a reduction to satisfiability in propositional logic (SAT). The advantage of this new algorithm is, on the one hand, that it allows us to employ highly optimized state-of-the-art SAT solvers when implementing an \(\mathcal{EL}\)-unification algorithm. On the other hand, this reduction provides us with a proof of the fact that \(\mathcal{EL}\)-unification is in NP that is much simpler than the one given in our previous paper on \(\mathcal{EL}\)-unification.


Description Logic Propositional Variable Horn Clause Concept Variable Concept Term 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2010

Authors and Affiliations

  • Franz Baader
    • 1
  • Barbara Morawska
    • 1
  1. 1.Theoretical Computer ScienceTU DresdenGermany

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