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 http://darq.sf.net/ .
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References
Prud’hommeaux, E., Seaborne, A.: SPARQL Query Language for RDF. W3C Recommendation (January 2008), http://www.w3.org/TR/rdf-sparql-query/
Florescu, D., Levy, A., Manolescu, I., Suciu, D.: Query optimization in the presence of limited access patterns. In: International conference on Management of data (SIGMOD), pp. 311–322. ACM, New York (1999)
Busse, S., Kutsche, R.D., Leser, U., Weber, H.: Federated information systems: Concepts, terminology and architectures. Technical Report Forschungsberichte des Fachbereichs Informatik 99-9, Technische Universität Berlin (1999)
Lakshmanan, L.V.S., Sadri, F., Subramanian, I.N.: SchemaSQL - a language for interoperability in relational multi-database systems. In: Vijayaraman, T.M., Buchmann, A.P., Mohan, C., Sarda, N.L. (eds.) 22th International Conference on Very Large Data Bases (VLDB), Mumbai (Bombay), India, September 1996, pp. 239–250 (1996)
Sheth, A.P., Larson, J.A.: Federated database systems for managing distributed, heterogeneous, and autonomous databases. ACM Comput. Surv. 22(3), 183–236 (1990)
Wiederhold, G.: Mediators in the architecture of future information systems. Computer 25(3), 38–49 (1992)
Stuckenschmidt, H., Vdovjak, R., Houben, G.-J., Broekstra, J.: Index structures and algorithms for querying distributed rdf repositories. In: WWW 2004 (2004)
Chen, H., Wang, Y., Wang, H., Mao, Y., Tang, J., Zhou, C., Yin, A., Wu, Z.: Towards a semantic web of relational databases: a practical semantic toolkit and an in-use case from traditional chinese medicine. In: 4th International Semantic Web Conference (ISWC), Athens, USA. LNCS, pp. 750–763. Springer, Heidelberg (2006)
Hartig, O., Heese, R.: The sparql query graph model for query optimization. In: 4th European Semantic Web Conference (ESWC), pp. 564–578 (2007)
Bernstein, A., Christoph Kiefer, M.S.: OptARQ: A SPARQL Optimization Approach based on Triple Pattern Selectivity Estimation. Technical Report ifi-2007.03, Department of Informatics, University of Zurich (2007)
Harth, A., Decker, S.: Optimized index structures for querying rdf from the web. In: Third Latin American Web Congress (LA-WEB), Washington, DC, USA, p. 71. IEEE Computer Society, Los Alamitos (2005)
Harris, S., Gibbins, N.: 3store: Efficient bulk rdf storage. In: PSSS - Practical and Scalable Semantic Systems (2003)
Kossmann, D.: The state of the art in distributed query processing. ACM Comput. Surv. 32(4), 422–469 (2000)
Manola, F., Miller, E.: RDF Primer, W3C Recommendation (2004), http://www.w3.org/TR/rdf-primer/
Pérez, J., Arenas, M., Gutierrez, C.: Semantics and Complexity of SPARQL. In: 4th International Semantic Web Conference (ISWC), Athens, GA, USA, pp. 30–43 (November 2006)
Haas, L.M., Kossmann, D., Wimmers, E.L., Yang, J.: Optimizing queries across diverse data sources. In: 23rd Int. Conference on Very Large Data Bases (VLDB), pp. 276–285. Morgan Kaufmann Publishers Inc., San Francisco (1997)
Selinger, P.G., Astrahan, M.M., Chamberlin, D.D., Lorie, R.A., Price, T.G.: Access path selection in a relational database management system. In: International conference on Management of data (SIGMOD), pp. 23–34. ACM Press, New York (1979)
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Quilitz, B., Leser, U. (2008). Querying Distributed RDF Data Sources with SPARQL. In: Bechhofer, S., Hauswirth, M., Hoffmann, J., Koubarakis, M. (eds) The Semantic Web: Research and Applications. ESWC 2008. Lecture Notes in Computer Science, vol 5021. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-68234-9_39
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DOI: https://doi.org/10.1007/978-3-540-68234-9_39
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