The Exelixis Lab (I12), Department of Computer Science, Technische Universität München, Boltzmannstr. 3, D-85748, Garching b. München, Germany. stamatak@cs.tum.edu|The Exelixis Lab (I12), Department of Computer Science, Technische Universität München, Boltzmannstr. 3, D-85748, Garching b. München, Germany. stamatak@cs.tum.edu