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A Query-driven Procedures for Hybrid MKNF Knowledge Bases
| Citations: | 10 - 10 self |
BibTeX
@MISC{Alferes_aquery-driven,
author = {José Júlio Alferes and Matthias Knorr and Terrance Swift},
title = {A Query-driven Procedures for Hybrid MKNF Knowledge Bases},
year = {}
}
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Abstract
Hybrid MKNF knowledge bases are one of the most prominent tightly integrated combinations of openworld ontology languages with closed-world (non-monotonic) rule paradigms. Based on the logic of minimal knowledge and negation as failure (MKNF), the definition of Hybrid MKNF is parametric on the description logic (DL) underlying the ontology language, in the sense that non-monotonic rules can extend any decidable DL language. Two related semantics have been defined for Hybrid MKNF: one that is based on the Stable Model Semantics for logic programs and one on the Well-Founded Semantics (WFS). Under WFS, the definition of Hybrid MKNF relies on a bottom-up computation that has polynomial data complexity whenever the DL language is tractable. Here we define a general query-driven procedure for Hybrid MKNF that is sound with respect to the stable model-based semantics, and sound and complete with respect to its WFS variant. This procedure is able to answer a slightly restricted form of conjunctive queries, and is based on tabled rule evaluation extended with an external oracle that captures reasoning within the ontology. Such an (abstract) oracle receives as input a query along with knowledge already derived, and replies with a (possibly empty) set of atoms, defined in the rules, whose truth would suffice to prove the initial query. With appropriate assumptions on the complexity of the abstract oracle, the general procedure maintains the data complexity of the WFS for Hybrid MKNF knowledge bases.
Keyphrases
hybrid mknf knowledge base hybrid mknf query-driven procedure minimal knowledge ontology language general query-driven procedure description logic stable model semantics polynomial data complexity initial query non-monotonic rule related semantics external oracle well-founded semantics decidable dl language general procedure dl language conjunctive query data complexity rule paradigm tabled rule evaluation logic program integrated combination appropriate assumption abstract oracle wfs variant openworld ontology stable model-based semantics bottom-up computation
