Revision with unchanged content. With the steadily increasing availability of information on the internet and in corporate databases, the demand for structured approaches to identifying and making use of relevant information is growing rapidly. This book provides an introduction on how heterogeneous data sources can be integrated to form a single source of information for a given information need. State of the art information retrieval methods are described and a workflow-based approach to data integration is introduced in this book. Besides theoretical foundations, the book provides details on the pracatical application of pattern-based workflows to retrieve the data which is required in a particular situation. The pattern-based approach for information retrieval can be used for applications in knowledge management and other areas where relevant information is stored in various data sources.