Add to ORKGI would like to dedicate this thesis to the soul of my late father Prof. Dr. Kamal Abd Alla Rizk, whom I wished so much that he would be around while presenting this research and during my graduation ceremony. I have to admit that if it were not for my father, I would not have considered going for the masters degree. I want to tell him that I miss him so much. iii Acknowledgements My first thanks and gratitude are for God who gave me the strength and persistence to finish this thesis. My second appreciation goes directly to Prof. Dr. Hoda Hosny for initially her acceptance to be the supervisor of this research. Also, for her sincere devotion and guidance based on deep knowledge and patience through all the years that I have worked with her....