Requirements Evolution: from Assumptions to Reality

Requirements evolution is a main driver for systems evolution. Traditionally, requirements evolution is associated to changes in the users' needs and environments. In this paper, we explore another cause for requirements evolution: assumptions. Requirements engineers often make assumptions stating, for example, that satisfying certain sub-requirements and/or correctly executing certain system functionalities would lead to reach a certain requirement. However, assumptions might be, or eventually become, invalid. We outline an approach to monitor, at runtime, the assumptions in a requirements model and to evolve the model to reflect the validity level of such assumptions. We introduce two types of requirements evolution: autonomic (which evolves the priorities of system alternatives based on their success/failure in meeting requirements) and designer-supported (which detects loci in the requirements model containing invalid assumptions and recommends designers to take evolutionary actions).