The Web Ontology Language OWL is currently the most prominent formalism for representing ontologies in Semantic Web applications. OWL is based on description logics, and automated reasoners are used to infer knowledge implicitly present in OWL ontologies. However, because typical description logics obey the classical principle of explosion, reasoning over inconsistent ontologies is impossible i...

This paper describes DLEJena, a practical reasoner for the OWL 2 RL profile that combines the forward-chaining rule engine of Jena and the Pellet DL reasoner. This combination is based on rule templates, instantiating at run-time a set of ABox OWL 2 RL/RDF Jena rules dedicated to a particular TBox that is handled by Pellet. The goal of DLEJena is to handle efficiently, through instantiated rule...

As part of the quest for a unifying logic for the Semantic Web Technology Stack, 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, w...

This paper describes the ODBA problem solution based on query rewriting techniques, introduces the DL-Lite logics for knowledge representation and the query rewriting algorithms for high-level data access. The RQR algorithm’s optimization capabilities are considered. KeywordsODBA;description logic; DL-Lite; query answering, query rewriting,OWL 2 QL

This chapter provides a self-contained first introduction to description logics (DLs). The main concepts and features are explained with examples before syntax and semantics of the DL SROIQ are defined in detail. Additional sections review light-weight DL languages, discuss the relationship to the Web Ontology Language OWL and give pointers to further reading.

This paper provides a self-contained first introduction to description logics (DLs). The main concepts and features are explained with examples before syntax and semantics of the DL SROIQ are defined in detail. Additional sections review lightweight DL languages, discuss the relationship to the OWL Web Ontology Language and give pointers to further reading.

In this poster, we propose to recast the idea of knowledge compilation into approximating OWL DL ontologies with DL-Lite ontologies, against which query answering has only polynomial data complexity. We identify a useful category of queries for which our approach also guarantees completeness. Furthermore, we paper report on the implementation of our approach in the ONTOSEARCH2 system.

We prove co-N2ExpTime-hardness for conjunctive query entailment in the description logicALCOIF , thus improving the previously known 2ExpTime lower bound. The result transfers to OWL DL and OWL2 DL, of whichALCOIF is an important fragment. A matching upper bound remains open.

The Web Ontology Language (OWL) adheres to the openworld assumption and can thus not be used for forms of nonmonotonic reasoning or defeasible inference, an acknowledged desirable feature in open Semantic Web environments. We investigate the use of the formalism of circumscriptive description logics (DLs) to realise defeasible inference within the OWL framework. By example, we demonstrate how r...

Let P be a named concept that is the partition which is divided into several concepts Ci. Then the partition is defined by introducing the following axioms (expressed in the standard DL syntax) as also be shown in Figure 1: P ≡ C0 C1 · · · Cn and Ci Cj = ⊥ for 0 ≤ i, j ≤ n, i = j. Note that some ontology languages such as OWL 2 [1] provides disjointness axioms as syntactical sugar to make the d...