@techreport{PredaSuchanekKasneciNeumannWeikum2009,
TITLE = {Coupling Knowledge Bases and Web Services for Active Knowledge},
AUTHOR = {Preda, Nicoleta and Suchanek, Fabian and Kasneci, Gjergji and Neumann, Thomas and Weikum, Gerhard},
LANGUAGE = {eng},
NUMBER = {MPI-I-2009-5-004},
LOCALID = {Local-ID: C1256DBF005F876D-BF2AB4A39F925BC8C125759800444744-PredaSuchanekKasneciNeumannWeikum2009},
YEAR = {2009},
DATE = {2009},
ABSTRACT = {We present ANGIE, a system that can answer user queries by combining<br>knowledge<br>from a local database with knowledge retrieved from Web services. If a user<br>poses a query that cannot be answered by the local database alone, ANGIE<br>calls<br>the appropriate Web services to retrieve the missing information. In<br>ANGIE,Web<br>services act as dynamic components of the knowledge base that deliver<br>knowledge<br>on demand. To the user, this is fully transparent; the dynamically acquired<br>knowledge is presented as if it were stored in the local knowledge base.<br>We have developed a RDF based model for declarative definition of functions<br>embedded in the local knowledge base. The results of available Web<br>services are<br>cast into RDF subgraphs. Parameter bindings are automatically constructed by<br>ANGIE, services are invoked, and the semi-structured information returned by<br>the services are dynamically integrated into the knowledge base<br>We have developed a query rewriting algorithm that determines one or more<br>function composition that need to be executed in order to evaluate a<br>SPARQL style<br>user query. The key idea is that the local knowledge base can be used to<br>guide the selection of values used as input parameters of function<br>calls. This is in<br>contrast to the conventional approaches in the literature which would<br>exhaustively<br>materialize all values that can be used as binding values for the input<br>parameters.},
TYPE = {Research Reports},
}