Over the past decade most of engineers, researchers, Institutions, standard organizations and businessmen had been faced with challenges on how to represent productivity functions for effort estimation in information system workflow development. Despite the fact that workflows are everywhere, only few reports about its development effort are available. Accurate workflow sizing is a very difficult task at conceptual state. This book proposes the proximity scoring measurement method to determine workflow size and to estimate workflow development effort with its knowledge retention effort. The approach is applied to case study. The approach of this book is scalable and easy to apply to evaluate workflow development effort. The implication of this work is that workflows can be estimated more precisely, helping to estimate the benefit of workflow reuse.