document: Piazza : data management infrastructure for semantic web applications The Semantic Web envisions a World Wide Web in which data is described with rich semantics and applications can pose complex queries . To this point , researchers have defined new languages for specifying meanings for concepts and developed techniques for reasoning about them , using RDF as the data model . To flourish , the Semantic Web needs to be able to accommodate the huge amounts of existing data and the applications operating on them . To achieve this , we are faced with two problems . First , most of the world 's data is available not in RDF but in XML ; XML and the applications consuming it rely not only on the domain structure of the data , but also on its document structure . Hence , to provide interoperability between such sources , we must map between both their domain structures and their document structures . Second , data management practitioners often prefer to exchange data through local point-to-point data translations , rather than mapping to common mediated schemas or ontologies . This paper describes the Piazza system , which addresses these challenges . Piazza offers a language for mediating between data sources on the Semantic Web , which maps both the domain structure and document structure . Piazza also enables interoperation of XML data with RDF data that is accompanied by rich OWL ontologies . Mappings in Piazza are provided at a local scale between small sets of nodes , and our query answering algorithm is able to chain sets mappings together to obtain relevant data from across the Piazza network . We also describe an implemented scenario in Piazza and the lessons we learned from it .
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