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Recent Advances in Integrating OWL and Rules (Technical Communication)
[chapter]

Matthias Knorr, David Carral Martínez, Pascal Hitzler, Adila A. Krisnadhi, Frederick Maier, Cong Wang

2012
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Lecture Notes in Computer Science
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As part of the quest for a unifying logic for the Semantic Web Technology Stack, 4 a central issue is finding suitable ways of integrating description logics based on the Web Ontology Language (OWL) with rule-based approaches based on logic programming. Such integration is difficult since naive approaches typically result in the violation of one or more desirable design principles. For example, while both OWL 2 DL and RIF Core (a dialect of the Rule Interchange Format RIF) are decidable, their
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... aive union is not, unless carefully chosen syntactic restrictions are applied. We report on recent advances and ongoing work by the authors in integrating OWL and rules. We take an OWL-centric perspective, which means that we take OWL 2 DL as a starting point and pursue the question of how features of rulebased formalisms can be added without jeopardizing decidability. We also report on incorporating the closed world assumption and on reasoning algorithms. This paper essentially serves as an entry point to the original papers, to which we will refer throughout, where detailed expositions of the results can be found. Rule-Extensions of OWL In [4], Grosof et al. describe a fragment of the description logic SHOIN (a.k.a. OWL 1 DL) which, if syntactically transferred to first-order predicate logic (FOL) in a straightforward way, results in a set of function-free Horn clauses, i.e. a Datalog program under FOL semantics. This naive approach has been subsequently lifted to OWL 2 DL and given rise to the OWL 2 RL fragment [10]. This work does not, however, address the problem of identifying the rules of Datalog (under FOL semantics) expressible in OWL and its variants, and indeed recent results, including the work on description logic rules by Krötzsch et al. [7], show that OWL 2 RL can be improved significantly in this respect. To formulate the recent findings, we first note that a directed graph G r can be constructed from any given binary Datalog rule r, i.e. a rule containing only unary and binary predicates. The nodes of G r are the variables occurring in the rule body of r, and there is exactly one directed edge between two variables x and y if there is at least one binary atom of the form P (x, y) appearing in the

doi:10.1007/978-3-642-33203-6_20
fatcat:l2l6wjeopvaalpiek33j2sqko4