1. Department of Computer Science, School of Computation, Information and Technology, Technical University of Munich, 85748 Garching, Germany
2. Artificial Intelligence and Intelligent Information Systems, University of Trier, 54296 Trier, Germany
3. German Research Center for Artificial Intelligence (DFKI), Branch University of Trier, 54296 Trier, Germany
4. Research Group Workflow Systems and Technology, Faculty of Computer Science, University of Vienna, 1090 Vienna, Austria
5. Research Centre for Information Systems Engineering (LIRIS), KU Leuven, Warmoesberg 26, 1000 Brussels, Belgium