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Revision with unchanged content. Web-based information systems, such as search engines, news portals, elec tronic markets and community sites, provide access to information origi nating from numerous information providers. The quality of provided infor mation varies as information providers have different levels of knowledge and different intentions. Users of web-based systems are therefore confron ted with the increasingly difficult task to select high quality information from the vast amount of Web-accessible information. How can information sys tems support users to distinguish high quality from low quality information? Which filtering mechanisms can be applied? How can filtering decisions be explained to the user? The book gives an overview about information quality assessment in context of web-based systems. Afterwards, a quality-driven information filtering framework is developed. The framework allows infor mation consumers to apply a wide range of different filtering policies. In order to facilitate the information consumers´ understanding of filtering decisions, the framework generates explanations why information satisfies a specific policy. The book targets Web developers who need to handle infor mation quality problems within their applications as well as researchers wor king on the topic.

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is a researcher at Freie Universität Berlin.His work focuses on questionsconcerning web-based information integrationsuch as information quality assessment,provenance tracking, and the representation of Web data. He initialized several open source software projects andcontributes to W3C standardization.

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