Division for Simulation of Biological Systems, ZBIT/WSI, Eberhard-Karls-Universität Tübingen, Germany. blum@informatik.uni-tuebingen.de|Division for Simulation of Biological Systems, ZBIT/WSI, Eberhard-Karls-Universität Tübingen, Germany. blum@informatik.uni-tuebingen.de|Division for Simulation of Biological Systems, ZBIT/WSI, Eberhard-Karls-Universität Tübingen, Germany. blum@informatik.uni-tuebingen.de