tel-00553143, version 1 - 6 Jan 2011 Acknowledgments First of all, countless thanks to Almighty Allah, Who has given me knowledge and courage to carry out this work. Secondly, I would like the readers to keep all the below-mentioned people in mind while reading this dissertation, without them this success would not have been possible. I would like to begin by thanking my Ph.D. advisors, Olivier Sentieys and Steven Derrien, for their guidance, understanding, patience, always believing in my capabilities and most importantly, their friendship during my Ph.D. at IRISA Rennes. They provided me different flavors of care as they were my bosses, advisors, friends and brothers from time to time. They have always helped me to not only grow as a researcher and developer but also an independent thinker and a better human being. It is my honour to have worked with them. I would also like to thank all my colleagues of CAIRN research team and administration staff at IRISA for creating such a pleasant work environment and for being there for me. In particular many thanks to Kevin Martin, Antoine Floch, Erwan Raffin, Laurent Perraudeau, Antoine Morvan, Naeem Abbas, Amit Kumar, Jeremie Guidoux, Loic Cloatre, Florent Berthelot, Georges Adouko, Maxime Naullet, Charles Wagner, François Charot, Christophe Wolinski, Patrice Quinton and Ludovic L’Hours with whom I worked closely and had many fruitful discussions. Many thanks to my colleagues at Lannion as well including Olivier Berder, Daniel Menard, Daniel Chillet, Sebastian Pillement, Emmanuel Casseau, Philippe Quemerais, Thomas Anger, Arnaud Carer, Vivek T.D., Shafqat Khan and others. I would also like to pay special thanks to CAIRN team-assistants Celine, Elise and Nadia for their support. Most importantly I would like to thank my parents, Abdul Hameed and Latifan Bibi, for their faith in me, encouraging me to be as ambitious as I wanted and supporting me in all my endeavors. It was under their watchful eye that I gained so much drive and ability to tackle challenges head on. A very special thanks goes to my siblings, nephews and nieces as well for being there for me all the time and cheering me up. I thank all my friends in France and in Pakistan for motivating me and regularly wishing me good luck. I am very grateful to all of them who made me feel at home, cared for and allowed me to worry only about my studies during my stay in France. I would also like to thank my teachers at Centre d’Etudede Langue of Colmar and at University of Nice Sophia-Antipolis. Finally I would like to express my indebtedness to all the jury members for spending their precious time to read and accept my work. This dissertation is dedicated to the light of useful knowledge that enlightens our lives.