Towards Variability Design as Decision Boundary Placement

Complex information systems have numerous design variables that are systematically decided upon during the design process. In high-variability systems, some of these decisions are left open and deferred to later stages. For example, in product line architectures, some decision variables are used to generate families of products with variations in features. In user-adaptive systems, the behavior of the system is determined at runtime, based on user characteristics and preferences. In this paper, we propose to characterize variability in terms of boundaries in design decision graphs which depict the space of alternatives. A design decision about variability, such as what choices should be left to the user and which ones should be fixed at which stage in the design process, is then a question of where to place that decision boundary along some path in the relevant decision graph.