Semantic integration became an attractive area of research in several disciplines, such as information integration, databases and ontologies. Huge amount of data is still stored in relational databases (RDBs) that can be used to build ontology, and the database cannot be used directly by the semantic web. Therefore, one of the main challenges of the semantic web is mapping relational databases ...

RDF knowledge graphs have attracted increasing attentions these years. However, due to the schema-free nature of RDF data, it is very difficult for users to have full knowledge of the underlying schema. Furthermore, the same kind of information can be represented in diverse graph fragments. Hence, it is a huge challenge to formulate complex SPARQL expressions by taking the union of all possible...

Contrary to earlier reports in literature, exhaustive forward inferencing is a feasible approach for practical RDF. It is sufficiently fast and the increase in necessary storage size is sufficiently small to make it work. Benefits of this approach are low-cost design and implementation, and very cheap query answering, since this task is reduced to simple lookup without inferencing. A potential ...

The W3C Web Ontology Language (OWL) provides the needed expressiveness formulation of complex concepts. However, the codification of an ontology is a thought formalization process that sometimes requires extensive knowledge and is often inaccessible laypersons. The G-OWL (for Graphical OWL) syntax has been designed to make easier the knowledge expression (compliant to OWL) in a graphical way. T...

Linked Data principles allow for processing SPARQL queries on-the-fly by dereferencing URIs. Link-traversal query approaches for Linked Data have the benefit of up-to-date results and decentralised execution, but operate only on explicit data from dereferenced documents, affecting recall. In this paper, we show how inferable knowledge— specifically that found through owl:sameAs and RDFS reasoni...

The problem of updating ontologies has received increased attention in recent years. In the approaches proposed so far, either the update language is restricted to (sets of) atomic updates, or, where the full SPARQL Update language is allowed, the TBox language is restricted to RDFS where no inconsistencies can arise. In this paper we discuss directions to overcome these limitations. Starting f...

Le web sémantique propose un jeu de langages permettant de publier et consommer des données liées et la sémantique des schémas de ces données : RDF, RDFS, OWL, SPARQL, etc. De plus en plus d’organisations privées et publiques participent à ce web de données en publiant dans ces langages des données ouvertes et leurs modèles de données non seulement sur le web ouvert mais aussi sur leurs intrane...

A vast amount of information sources is stored as relationallike data and inaccessible to RDFS-based systems. In this paper we describe an approach to integration such information sources with RDFSaware systems. The proposed solution is purely RDFS-based. We use RDF/S as a mechanism to specify and perform linking of relational data and a predefined domain ontology. The approach is transformatio...

ERDF stable model semantics is a recently proposed semantics for ERDF ontologies and a faithful extension of RDFS semantics on RDF graphs. In this paper, we elaborate on the computability and complexity issues of the ERDF stable model semantics. We show that decidability under this semantics cannot be achieved, unless ERDF ontologies of restricted syntax are considered. Therefore, we propose a ...

In this paper we present a method and an implementation for creating and processing semantic events from interaction with Web pages which opens possibilities to build event-driven applications for the (Semantic) Web. Events, simple or complex, are models for things that happen e.g., when a user interacts with a Web page. Events are consumed in some meaningful way e.g., for monitoring reasons or...