Appreciation is due to many people who have helped, often without knowing they were doing so, for inspiration, exhortation, and consolation throughout the three and bit years it has taken to create this work.

Special thanks go to Jon Kerridge who started it all off, and who had enough faith in me to take me on as a student in the first place. He gave me encouragement, advice, and the space to develop the ideas contained in this thesis (which is very different from the original research proposal and the work which I initially started on).

For professional help beyond the call of duty, I especially thank Paul Thompson currently at the National Transputer Support Centre, Sheffield. Also thanks to Romola Guiton and Roger England at the same institute for interesting discussions and comments. Other people who have commented upon, discussed, helped with, argued about, agreed and disagreed with, to a greater or lesser extent, the ideas presented here include in particular (in alphabetical order) Bill Edisbury, Dave Robson, Geoff Barratt, Geoff Sharman, Gilbert Laycock, Gordon Manson, Jeff Jones, Ken Moody, Maria Bielikova, Mike Stannett, Niall McCarroll, Paddy Nixon, Paul Murray, Peter Croll, Rob Waltham and Siobhan North. Thanks to one and all.

Drafts of this thesis were proofed by Carl Birkinshaw, Jeff Jones and Niall McCarroll for which I am grateful.

All the librarians at ASL who have been kind, helpful and friendly. Thank you.

Personal thanks are due to numerous people, specially Josie, Niall, and Tatt for support in times of crisis. To everyone else who has made the past three years memorable, interesting and enjoyable, thanks.

Finally, acknowledgement is made of the funding under a SERC CASE award, without which I would not have been able to do this work. Also thanks to Hewlett Packard for their financial contribution to the award.

Dedicated to my parents