Writing and, more importantly, completing this thesis was a time-consuming and not always pleasant process, especially in times when I was stuck, or when things were just not going as smoothly as I would have liked. During the whole project though, I could always count on a few people, and I will always be grateful for their expertise, support, and most importantly their help and friendship.

    First of all, I would very much like to thank Rob Barrett, Steve Ihde and Sabra-Anne Kelin. Rob was my thesis advisor at Almaden, and has a great way of working with people, and explaining things to them. Rob helped me to overcome problems by providing very valuable input and advice to solve them. I always enjoyed working with Rob and I am really looking forward to keep working with him. Many thanks also go to Steve Ihde, my co-worker and close friend. Steve is one of these amazing people, whom you can always ask if you have a question. And even more amazingly, Steve almost always knows the answers. Sabra-Anne has been a good friend and great officemate, and has put a lot of work in reviewing my paper. I really enjoyed our discussions and I really appreciate her efforts in teaching me the details of the English-American language.

    I would also like to thank my thesis advisor at the University of Applied Sciences in Hamburg, Professor Kai von Luck. He encouraged and helped me to go abroad and always supported me during my two stays at the Almaden Research Lab. His expertise as well as our few, but very fruitful discussions (on the phone) during my thesis project were tremendously helpful. I hope he will have as much fun reading this thesis as I had working on it.

    Moreover, I would like to say thanks to the members of the USER group, especially to Paul Maglio, and my managers Mike Wirth and Jim Spohrer.

    Last but not least, on a more personal note, I would like thank my wife Sonja and my family for all the love and support they have given me over the years.

April 9, 1999 · Jörg Meyer ·