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Auflistung nach Autor:in "Langegger, Andreas"

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  • Zeitschriftenartikel
    A Database Perspective on Consuming Linked Data on the Web
    (Datenbank-Spektrum: Vol. 10, No. 2, 2010) Hartig, Olaf; Langegger, Andreas
    During recent years an increasing number of data providers adopted the Linked Data principles for publishing and connecting structured data on the Web, thus creating a globally distributed dataspace—the Web of Data. While the execution of structured, SQL-like queries over this dataspace opens possibilities not conceivable before, query execution on the Web of Data poses novel challenges. These challenges provide great opportunities for the database community.In this article we introduce the concept of Linked Data and discuss different approaches to query the Web of Data. Our goal is to provide a general understanding of this new research area and of the challenges and open issues that must be addressed.
  • Konferenzbeitrag
    SemWIQ – Semantic Web Integrator and Query Engine
    (INFORMATIK 2008. Beherrschbare Systeme - dank Informatik. Band 2, 2008) Langegger, Andreas; Wöß, Wolfram
    One of the most popular applications of Semantic Web technology is the integration of data from distributed locations over the Web. With wrappers, screen scrapers, and information extraction tools it is possible to access, merge, and reason over RDF data from various different, heterogeneous sources. SPARQL can be used to access RDF data in a declarative manner and as will be shown, it can also be used to virtually integrate distributed RDF graphs. In this contribution a mediator-wrapper based middleware is shown which virtually integrates distributed, heterogeneous data sources based on RDF and a slightly modified SPARQL algebra. Schema information available in RDF Schema and OWL vocabularies is used for query federation and optimization. Compared to traditional data integration systems, SemWIQ can fully exploit the semantics of available RDF data. Additionally, RDF has many interesting properties which provide advanced query capabilities based on OWL DL inference.