Assessment of design patterns during software reengineering: lessons learned from a large commercial project

Design patterns have been eagerly adopted by software developers in recent years. There is ample evidence that patterns can have a beneficial impact on software quality, but in some cases patterns have been inappropriately applied due to a lack of experience. The paper reports on a large commercial project where the uncontrolled use of patterns has contributed to severe maintenance problems. As a result, a substantial reengineering effort was undertaken, that led to the identification of a number of inappropriately applied patterns. At first glance the elimination of these patterns appears to be desirable, but often they are tightly coupled to other software artefacts, so that their removal is economically not viable.