Alexander Block business informatics C C++ Comprehensive University Essen curriculum vitae diploma thesis Distance learning university in Hagen doctorand downloads ECMS email Enterprise Content Management System entries entry Extensible Metadata Platform eZ Publish eZ Systems friends FritzBox gentoo google graduant GraMToR Graphical Modeling Tool for RDF guest book Immersive Imaging life career Linux markup message PHP php upload progress projection system RDF RDFHandle Resource Description Framework search search engine University Duisburg-Essen VIEW Virtual Immersive Environment Workplace XML XMP XMP4PHP