Revision with unchanged content. Over the course of the past 15 years the business environment has significantly changed. Enterprises are no longer limited to local markets. In order to work effectively, they have to be agile and constantly adapt their business processes. Traditional Workflow Management software solutions are limited in their support for this kind of environment, often working under the precondition of standardized, repeatable processes. Current research is focused on a new generation of Workflow Management Systems that allows modifications to individual workflows even while they are undergoing execution. Contrary to traditional approaches such applications must provide concepts for suspension, locking and recovery that are minimally invasive but yet able to ensure consistency of modifications. This book provides a detailed overview of the motivation for this kind of system as well as an architectual concept for the implementation that covers the most frequently used workflow patterns.