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DBpedia is a community effort to extract structured information from Wikipedia and to make this information available on the Web. DBpedia allows you to ask sophisticated queries against datasets derived from Wikipedia and to link other datasets on the Web to Wikipedia data. We describe the extraction of the DBpedia datasets, and how the resulting(More)
The DBpedia project is a community effort to extract structured information from Wikipedia and to make this information accessible on the Web. The resulting DBpedia knowledge base currently describes over 2.6 million entities. For each of these entities, DBpedia defines a globally unique identifier that can be dereferenced over the Web into a rich RDF(More)
D2R Server is a tool for publishing the content of relational databases on the Semantic Web. Database content is mapped to RDF by a declarative mapping which specifies how resources are identified and how property values are generated from database content. Based on this mapping, D2R Server allows Web agents to retrieve RDF and XHTML representations of(More)
Developers of Semantic Web applications face a challenge with respect to the decentralised publication model: how and where to find statements about encountered resources. The " linked data " approach mandates that resource URIs should be de-referenced to return resource metadata. But for data discovery linkage itself is not enough, and crawling and(More)
The Resource Description Framework RDF allows you to describe web documents and resources from the real world—people, organisations, things—in a computer-processable way. Publishing such descriptions on the web creates the semantic web. URIs are very important as the link between RDF and the web. This article presents guidelines for their effective use. We(More)
We demonstrate Sig.ma, both a service and an end user application to access the Web of Data as an integrated information space. Sig.ma uses an holistic approach in which large scale semantic web indexing, logic reasoning, data aggregation heuristics, ad hoc ontology consolidation, external services and responsive user interaction all play together to(More)
The SPARQL query language for RDF provides Semantic Web developers with a powerful tool to extract information from large datasets. This report describes a transformation from SPARQL into the relational algebra, an abstract intermediate language for the expression and analysis of queries. This makes existing work on query planning and optimization available(More)
Web-based information systems, such as search engines, news portals, and community sites, provide access to information originating from numerous information providers. The quality of provided information varies as information providers have different levels of knowledge and different intentions. Users of web-based systems are therefore confronted with the(More)
The RDF Book Mashup demonstrates how Web 2.0 data sources like Amazon, Google and Yahoo can be integrated into the Semantic Web. Following the principles of linked data, the RDF Book Mashup makes information about books, their authors, reviews, and on-line bookstores available on the Semantic Web. This information can be used by RDF browsers and crawlers,(More)