Jos de Bruijn

IJCAI Conference 2009 Conference Paper

• Inanc Seylan
• Enrico Franconi
• Jos de Bruijn

We consider query answering on Description Logic (DL) ontologies with DBoxes, where a DBox is a set of assertions on individuals involving atomic concepts and roles called DBox predicates. The extension of a DBox predicate is exactly defined in every interpretation by the contents of the DBox, i. e. , a DBox faithfully represents a database whose table names are the DBox predicates and the tuples are the DBox assertions. Our goals are (i) to find out whether the answers to a given query are solely determined by the DBox predicates and, if so, (ii) to find a rewriting of the query in terms of them. The resulting query can then be efficiently evaluated using standard database technology. We have that (i) can be reduced to entailment checking and (ii) can be reduced to finding an interpolant. We present a procedure for computing interpolants in the DL ALC with general TBoxes. We extend the procedure with standard tableau optimisations, and we discuss abduction as a technique for amending ontologies to gain definability of queries of interest.

KR Conference 2008 Conference Paper

Embedding Approaches to Combining Rules and Ontologies into Autoepistemic Logic

• Jos de Bruijn
• Thomas Eiter
• Hans Tompits

The combination of rules and ontologies has a central role in the ongoing development of the Semantic Web. In previous work, autoepistemic logic (AEL) was advocated as a uniform host formalism to study different such combinations, enabling comparisons on a common basis. In this paper, we continue this line of research and investigate different embeddings of major proposals to combine rules and ontologies into first-order autoepistemic logic (FO-AEL). In particular, we present embeddings for dl-programs, r-hybrid knowledge bases, and hybrid MKNF knowledge bases, which are representatives of different combination types. We study the embeddings in the context of FO-AEL under the standard-names assumption, but we also discuss variants using the any- and all-names semantics. Our results provide interesting insights into the properties of the discussed combination formalisms.

IJCAI Conference 2007 Conference Paper

• Jos de Bruijn
• Thomas Eiter
• Axel Polleres
• Hans Tompits$

In the context of the Semantic Web, several approaches to the combination of ontologies, given in terms of theories of classical first-order logic, and rule bases have been proposed. They either cast rules into classical logic or limit the interaction between rules and ontologies. Autoepistemic logic (AEL) is an attractive formalism which allows to overcome these limitations, by serving as a uniform host language to embed ontologies and nonmonotonic logic programs into it. For the latter, so far only the propositional setting has been considered. In this paper, we present several embeddings of normal and disjunctive non-ground logic programs under the stable-model semantics into first-order AEL, and compare them in combination with classical theories, with respect to stable expansions and autoepistemic consequences. Our results reveal differences and correspondences of the embeddings and provide a useful guidance in the choice of a particular embedding for knowledge combination.