Frank van Harmelen

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The OWL Web Ontology Language is a new formal language for representing ontologies in the Semantic Web. OWL has features from several families of representation languages, including primarily Description Logics and frames. OWL also shares many characteristics with RDF, the W3C base of the Semantic Web. In this paper we discuss how the philosophy and(More)
RDF and RDF Schema are two W3C standards aimed at enriching the Web with machine-processable semantic data. We have developed Sesame, an architecture for efficient storage and expressive querying of large quantities of metadata in RDF and RDF Schema. Sesame’s design and implementation are independent from any specific storage device. Thus, Sesame can be(More)
The expressivity of RDF and RDF Schema that was described in [12] is deliberately very limited: RDF is (roughly) limited to binary ground predicates, and RDF Schema is (again roughly) limited to a subclass hierarchy and a property hierarchy, with domain and range definitions of these properties. However, the Web Ontology Working Group of W3C identified a(More)
The development of the Semantic Web, with machine-readable content, has the potential to revolutionize the World Wide Web and its use. In A Semantic Web Primer Grigoris Antoniou and Frank van Harmelen provide an introduction and guide to this emerging field, describing its key ideas, languages, and technologies. Suitable for use as a textbook or for(More)
have investigated them. More recently, the notion of an ontology is becoming widespread in fields such as intelligent information integration, cooperative information systems, information retrieval, electronic commerce, and knowledge management. Ontologies are becoming popular largely because of what they promise: a shared and common understanding that(More)
Currently computers are shifting from being a single isolated device to being an entry point in a world wide network of information exchange and business transactions. Therefore, support in data, information, and knowledge exchange is becoming a key issue in current computer technology. Providing shared and common domain structures becomes essential.(More)
representation techniques. T he World Wide Web is possible because a set of widely established standards guarantees interoperability at various levels. Until now, the Web has been designed for direct human processing, but the next-generation Web, which Tim Berners-Lee and others call the “Semantic Web,” aims at machine-processible information.1 The Semantic(More)
Ontologies are shared models of a domain that encode a view which is common to a set of different parties. Contexts are local models that encode a party’s subjective view of a domain. In this paper we show how ontologies can be contextualized, thus acquiring certain useful properties that a pure shared approach cannot provide. We say that an ontology is(More)
We address the problem of scalable distributed reasoning, proposing a technique for materialising the closure of an RDF graph based on MapReduce. We have implemented our approach on top of Hadoop and deployed it on a compute cluster of up to 64 commodity machines. We show that a naive implementation on top of MapReduce is straightforward but performs badly(More)
RDF and RDF Schema provide the first W3C standard to enrich the Web with machine-processable semantic data. However, to be able to use this semantic data, a scalable, persistent RDF store and a powerful query engine using an expressive query language are needed. Sesame is an extensible architecture implementing both of these. Sesame can be based on(More)