An approach to manage variance in legacy systems

Different market areas set different requirements on software-intensive products. A careful domain analysis yields the predictable variance that can be managed at the architectural and design levels, but the unpredictable variance that is detected only during the maintenance phase is usually managed at the implementation level, due to the high costs of the system re-design or re-architecting. Thus, most legacy systems contain a lot of unpredictable variance in the source code, e.g. in the form of cluttering it with pre-processor directives. The weak overlay technique is a promising reverse engineering approach to abstracting, comprehending, maintaining and re-designing legacy software containing various types of variance.