First of all I would like to thank my supervisors, Dr. Axel-Cyrille Ngonga Ngomo and Prof. Klaus-Peter Fähnrich, without whom I could not have started my Ph.D. at the Leipzig University.
Special thanks to my direct supervisor Dr. Axel-Cyrille Ngonga Ngomo, with whom I have started work on my Ph.D. proposal submitted to Deutscher Akademischer Austauschdienst (DAAD), in order to pursue my Ph.D. at the Agile Knowledge Engineering and Semantic Web (AKSW) group. He has continuously supported me throughout my Ph.D. work, giving advices and recommendations for further research steps. His comments and notes were very helpful for me particularly during the writing of the papers we published together. I would like to thank him also for proofreading this thesis and for his helpful feedback, which led to improving the quality of that thesis. Special thanks also to thank Prof. Sören Auer, whom I have first contacted asking for a vacancy to conduct my Ph.D. research at his research group. I am thankful to Dr. Jens Lehman for valuable discussions during my Ph.D. work
I would like also to thank Prof. Klaus-Peter Fähnrich, for the regular follow-up meetings he has managed in order to evaluate the performance of all Ph.D. students. During these meetings, he has proposed several directions for me and for other Ph.D. students as well, on how to deepen and extend our research points. I would like to thank all of my colleagues in the Semantic Abstraction (SIMBA) group, for providing me with their useful comments and guidelines, especially during the initial phase of my Ph.D.
I would like to dedicate this work to the souls of my parents, without whom I could not do anything in my life. With their help and support, I could take my first steps in my scientific career. Special thanks goes to all my family members and my friend Ahsan Rasheed.