Information Quality Assessment Policies in the Context of Open Information Systems Newer developments in the areas of Enterprise Data Integration and Knowledge Management are aiming at using information from a large number of autonomous data sources inside the company, from partner organizations and from the Web. Integrating data from independent sources raises questions of data quality and data trustworthiness. Before information should be used, its quality has to be assessed according to task-specific criteria. The goal of the thesis is to develop and evaluate a quality-driven information filtering framework which supports users in their decision whether to trust or to distrust information. The main objective of the framework is to support a wide range of different reputation-, context- and content-based quality assessment policies. In order to faziliate the user’s understanding of the filtering decisions, the framework creates explanations why data should be trusted. The concepts developed in this thesis are implmented as part of the TriQL.P Semantic Web browser and are evaluated in a financial and a scientific data integration scenario.