This book represents a modern and realistic approach to systems development methodologies by examining the usage of such methodologies in practice. It is now accepted that methodologies are not often followed as prescibed in practice. This book explains why this is so, and describes the extent and nature of thier usage.The book covers the emergence and evolution of systems development methodologies, and descibes and anaysis the methodologies in detail. It presents the pros and cons of the use of methodologies and provides empirical evidence on thier actual use.