Queries to hybrid MKNF knowledge bases through oracular tabling

José Júlio Alferes, Matthias Knorr, Terrance Swift

Research output: Chapter in Book/Report/Conference proceedingConference contribution

10 Scopus citations


An important issue for the Semantic Web is how to combine open-world ontology languages with closed-world (non-monotonic) rule paradigms. Several proposals for hybrid languages allow concepts to be simultaneously defined by an ontology and rules, where rules may refer to concepts in the ontology and the ontology may also refer to predicates defined by the rules. Hybrid MKNF knowledge bases are one such proposal, for which both a stable and a well-founded semantics have been defined. The definition of Hybrid MKNF knowledge bases is parametric on the ontology language, in the sense that non-monotonic rules can extend any decidable ontology language. In this paper we define a query-driven procedure for Hybrid MKNF knowledge bases that is sound with respect to the original stable model-based semantics, and is correct with respect to the well-founded semantics. This procedure is able to answer conjunctive queries, and is parametric on an inference engine for reasoning in the ontology language. Our procedure is based on an extension of a tabled rule evaluation to capture reasoning within an ontology by modeling it as an interaction with an external oracle and, with some assumptions on the complexity of the oracle compared to the complexity of the ontology language, maintains the data complexity of the well-founded semantics for hybrid MKNF knowledge bases.

Original languageEnglish (US)
Title of host publicationThe Semantic Web, ISWC 2009 - 8th International Semantic Web Conference, ISWC 2009, Proceedings
PublisherSpringer Verlag
Number of pages16
ISBN (Print)364204929X, 9783642049293
StatePublished - 2009
Externally publishedYes
Event8th International Semantic Web Conference, ISWC 2009 - Chantilly, VA, United States
Duration: Oct 25 2009Oct 29 2009

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume5823 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other8th International Semantic Web Conference, ISWC 2009
Country/TerritoryUnited States
CityChantilly, VA

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)


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