document: Querying for meta knowledge The Semantic Web is based on accessing and reusing RDF data from many different sources , which one may assign different levels of authority and credibility . Existing Semantic Web query languages , like SPARQL , have targeted the retrieval , combination and reuse of facts , but have so far ignored all aspects of meta knowledge , such as origins , authorship , recency or certainty of data , to name but a few . In this paper , we present an original , generic , formalized and implemented approach for managing many dimensions of meta knowledge , like source , authorship , certainty and others . The approach re-uses existing RDF modeling possibilities in order to represent meta knowledge . Then , it extends SPARQL query processing in such a way that given a SPARQL query for data , one may request meta knowledge without modifying the original query . Thus , our approach achieves highly flexible and automatically coordinated querying for data and meta knowledge , while completely separating the two areas of concern .
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