Querying Distributed RDF Data Sources with SPARQL

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Querying Distributed RDF Data Sources with SPARQL (2008)

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by Bastian Quilitz , Ulf Leser

Venue:	In Proceedings of the 5th European Semantic Web Conference (ESWC2008
Citations:	132 - 0 self

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@INPROCEEDINGS{Quilitz08queryingdistributed,
    author = {Bastian Quilitz and Ulf Leser},
    title = {Querying Distributed RDF Data Sources with SPARQL},
    booktitle = {In Proceedings of the 5th European Semantic Web Conference (ESWC2008},
    year = {2008}
}

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Abstract

Abstract. Integrated access to multiple distributed and autonomous RDF data sources is a key challenge for many semantic web applications. As a reaction to this challenge, SPARQL, the W3C Recommendation for an RDF query language, supports querying of multiple RDF graphs. However, the current standard does not provide transparent query federation, which makes query formulation hard and lengthy. Furthermore, current implementations of SPARQL load all RDF graphs mentioned in a query to the local machine. This usually incurs a large overhead in network traffic, and sometimes is simply impossible for technical or legal reasons. To overcome these problems we present DARQ, an engine for federated SPARQL queries. DARQ provides transparent query access to multiple SPARQL services, i.e., it gives the user the impression to query one single RDF graph despite the real data being distributed on the web. A service description language enables the query engine to decompose a query into sub-queries, each of which can be answered by an individual service. DARQ also uses query rewriting and cost-based query optimization to speed-up query execution. Experiments show that these optimizations significantly improve query performance even when only a very limited amount of statistical information is available. DARQ is available under GPL License at

Keyphrases

rdf data source legal reason real data sparql load w3c recommendation autonomous rdf data source network traffic service description language individual service sparql service federated sparql query speed-up query execution single rdf graph integrated access many semantic web application present darq rdf query language multiple rdf graph key challenge statistical information large overhead local machine current implementation query rewriting transparent query federation limited amount query formulation current standard query performance cost-based query optimization rdf graph gpl license query engine

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