Towards engineered architecture evolution

Architecture evolution, a key aspect of software evolution, is typically done in an ad hoc manner, guided only by the competence of the architect performing it. This process lacks the rigor of an engineering discipline. In this paper, we argue that architecture evolution must be engineered - based on rational decisions that are supported by formal models and objective analyses. We believe that evolutions of a restricted form - close-ended evolution, where the starting and ending design points are known a priori - are amenable to being engineered. We discuss some of the key challenges in engineering close-ended evolution. We present a conceptual framework in which an architecture evolutionary trajectory is modeled as a sequence of steps, each captured by an operator. The goal of our framework is to support exploration and objective evaluation of different evolutionary trajectories. We conclude with open research questions in developing this framework.