Note:
The Acrobat version of the thesis is slightly different from the original printed version in that the pagination is not quite the same. This is due to differences between the Acrobat printer driver and the driver used to print the hardcopy version. The content is entirely the same, but overall, the PDF version has one more page (251 vs 250) and some sections appear on different pages from those in the hardcopy version.

Paul Vickers
School of Computing and Mathematical Sciences
Liverpool John Moores University
Byrom Street
Liverpool L3 3AF
UK

email p.vickers@livjm.ac.uk
Web www.cms.livjm.ac.uk/paulvickers