Department of Computer Science, Technical University of Munich Boltzmannstrasse 3, D-85748 München, Germany. stamatak@cs.tum.edu|Department of Computer Science, Technical University of Munich Boltzmannstrasse 3, D-85748 München, Germany. stamatak@cs.tum.edu|Department of Computer Science, Technical University of Munich Boltzmannstrasse 3, D-85748 München, Germany. stamatak@cs.tum.edu