Applied Computer Science, Faculty of Technology, Bielefeld University D-33594 Bielefeld, Germany. fzoellne@techfak.uni-bielefeld.de|Applied Computer Science, Faculty of Technology, Bielefeld University D-33594 Bielefeld, Germany. fzoellne@techfak.uni-bielefeld.de|Applied Computer Science, Faculty of Technology, Bielefeld University D-33594 Bielefeld, Germany. fzoellne@techfak.uni-bielefeld.de|Applied Computer Science, Faculty of Technology, Bielefeld University D-33594 Bielefeld, Germany. fzoellne@techfak.uni-bielefeld.de