Systems reengineering patterns

Abstract

The reengineering of legacy systems - by which we mean those that have value and yet `significantly resist modification and evolution to meet new and constantly changing business requirements' - is widely recognized as one of the most significant challenges facing software engineers. The problem is widespread, affecting all kinds of organizations; serious, as failure to reengineer can hamper an organization's attempts to remain competitive; and persistent, as there seems no reason to be confident that today's new systems are not also tomorrow's legacy systems. This paper argues: 1. that the main problem is not that the necessary expertise does not exist, but rather, that it is hard for software engineers to become expert; 2. that the diversity of the problem domain poses problems for conventional methodological approaches; and 3. that an approach via systems reengineering patterns can help. We support our contention by means of some candidate patterns drawn from our own experience and published work on reengineering. We discuss the scope of the approach, how work in this area can proceed, and in particular how patterns may be identified and confirmed.