The web has brought fundamentally new challenges to data management. The key features that distinguish web data from traditional database applications are its structure - usually described by mark-up languages, such as XML - and its dynamic nature. The FOX research programme will study these challenges in detail and investigate ways to master them. To this end, FOX aims at a paradigm shift in the modelling of internet data. It will provide foundations of dynamic and data-oriented features of the Web, and come up with new efficient algorithms for organising, transforming, and querying Web content. Some of the prospective insights are expected to have a significant impact on the next generation of XML and Web standards. To achieve these general goals, FOX will work on a number of specific tasks. It will identify and investigate the infrastructure needed for document, schema, and constraint management for XML data with special emphasis on the handling of data and its constraints. Furthermore, the corresponding reasoning tasks will be studied. It will develop new techniques and algorithms for schema mapping, Web data exchange and for improving query evaluation by making use of schema information. These investigations will take into account that documents and schemas change over time and are distributed across multiple sites. A special focus will be on automated decision-making and on safety aspects, including verification of data-driven web services and run-time analysis. New techniques and algorithms for handling missing data and metadata in XML documents will be developed based on uncertainty management, on the one hand, and automatic recovery, on the other hand. Finally, FOX will develop a software library with prototypical implementations.