The impact of environmental evolution on requirements changes

We describe a case study of requirements changes due to an evolving environment. The Congruence Evaluation System was a proof of concept (CES POC) system which was part of a constantly evolving environment, and this change in the environment dictated the fitness of the CES POC system in the environment. The system served excellently for basic research purposes, but failed seriously in the long-term goal of evolvability with the set of coexisting research tools. We assessed the state of the system requirements, as well as that of the environment, at different times during system development and redevelopment. From this assessment we gained a detailed insight into how environmental evolution affects system survivability in terms of requirements changes. In this case study, we also found some empirical support for Lehman's (Lehman and Ramil, 2001) seventh law of software evolution, which has until now, neither been empirically supported nor refitted.