The Semantic Web initiative defines important challenges for knowledge representation and database systems. Recently, several standards for representation languages have been proposed (RDF, DAML+OIL, OWL). We briefly discuss the logical basis of these representation languages by referring to description logic (DL) inferences systems. By introducing the DL inference system Racer we demonstrate t...

Ontology-based modeling of Clinical Practice Guidelines (CPG) is a well-established approach to computerize CPG for execution in clinical decision support systems. Many CPG computerization approaches use the Web Ontology Language (OWL) to represent the CPG’s knowledge, but they do not exploit its reasoning services to execute the CPG. In this paper, we present our CPG execution approach that le...

Representing the Foundational Model of Anatomy (FMA) in OWL 2 is essential for semantic interoperability. The paper describes the method and tool used to formalize the FMA in OWL 2. One main strength of the approach is to leverage OWL 2 expressiveness and naming conventions of the native FMA to explicit some implicit semantics, meanwhile improving its ontological model and fixing some errors. A...

In this article, we define and study the problem of exchanging knowledge between a source and a target knowledgebase (KB), connected through mappings. Differently from the traditional database exchange setting, which considersonly the exchange of data, we are interested in exchanging implicit knowledge. As representation formalism we useDescription Logics (DLs), thus assuming that t...

We investigate an extension of Description Logics (DL) with higher-order capabilities, based on Henkin-style semantics. Our study starts from the observation that the various possibilities of adding higher-order constructs to a DL form a spectrum of increasing expressive power, including domain metamodeling, i.e., using concepts and roles as predicate arguments. We argue that higher-order featu...

Some of the applications of OWL and RDF (e.g. biomedical knowledge representation and semantic policy formulation) call for extensions of these languages with nonmonotonic constructs such as inheritance with overriding. Nonmonotonic description logics have been studied for many years, however no practical such knowledge representation languages exist, due to a combination of semantic difficulti...

We study the problem of evolution for Knowledge Bases (KBs) expressed in Description Logics (DLs) of the DL-Lite family. DL-Lite is at the basis of OWL 2 QL, one of the tractable fragments of OWL 2, the recently proposed revision of the Web Ontology Language. We propose some fundamental principles that KB evolution should respect. We review known model and formula-based approaches for evolution...

An important approach to query answering over OWL ontologies is via rewriting the input ontology (and query) into a new set of axioms that are expressed in logics for which scalable query answering algorithms exist. This approach has been studied for many important fragments of OWL like SHIQ, Horn-SHIQ, OWL 2 QL, and OWL 2 EL. An important family of rewriting algorithms is the family of resolut...

We present Owlgres, a DL-Lite reasoner implementation written for PostgreSQL, a mature open source database. Owlgres is an OWL reasoner that provides consistency checking and conjunctive query services, supports DL-LiteR as well as the OWL sameAs construct, and is not limited to PostgreSQL. We discuss the implementation with special focus on sameAs and the supported subset of the SPARQL languag...

An important approach to query answering over OWL ontologies is via rewriting the input ontology (and query) into a new set of axioms that are expressed in logics for which scalable query answering algorithms exist. This approach has been studied for many important fragments of OWL like SHIQ, Horn-SHIQ, OWL 2 QL, and OWL 2 EL. An important family of rewriting algorithms is the family of resolut...