Acknowledgements

First I would like to thank my family: my wife, Thuy, for her forever love, companionship and years long support and encouragement throughout the best and hardest times; my two sons Khoa (7yrd) and Khiem (4yrd) for their being good boys and understanding that dad is busy on his research and not having enough time to play with them. I thank my widowed mother Chuyen and my grand mother Lien for their nurturing me and my two sisters Nhan and An when my dad passed away as a result of the Vietnam war when I was only 4 year old. These two women have the most influence in my life. Without their support, affection and love throughout the hardest times, I would not be the person who wrote this thesis. There are many people that have earned my great deal of gratitude for their contribution to my growth as a researcher in graduate school. First of all, I want to thank my advisor, William Schuler. I could not get this far into writing this thesis without his years long supports and encouragements. He is always there for me through the good times and the bad times on my graduate school journey. Without him, I would have given up after a couple unsuccessful tries to push a paper published, and would never see the bright light when we finally got the Best Paper Award at COLING 2012. He is the one who took the responsibility and went extra mile