Acknowledgements

I am deeply grateful to my supervisor and teacher Prof. Johann Eder who made this dissertation initially possible, for his invaluable guidance, endless patience, perfectionism and generosity. I have not only learned a lot about computer sciences but also a lot about good personality. A special thank to Prof. Erich Schikuta for peer-reviewing of this dissertation and for his support and friendliness. I wish to thank both Prof. Johann Eder and Prof. Erich Schikuta as heads of the depart-ment during writing of this dissertation for providing an excellent working atmosphere. I owe a special note of gratitude to my colleagues at the Dept. of Knowledge and Business Engineering of the University of Vienna for their support, feedback, answering my questions, proofreading and a very friendly atmosphere at work. I want to extend many thanks to the team of the European project WS-Diamond for their cooperation. I would like to thank Dr. Marek Lehmann and Dr. Horst Pichler for their collaboration and cooperation. I would like to acknowledge those who directly and indirectly supported this work but are not listed here, specially my friends. Last but definitely not the least, I would like to specially thank my family for being a constant source of support, love and patience and their understanding for my tight schedule. This dissertation is funded by the European Commission and logistically supported b