Modern societies are pervaded by computerized, heterogeneous devices designed for specific purposes, but also more and more often capable of interacting with other devices for entirely different purposes. For example, a cell phone could be used to purchase a train ticket on-line that could later be printed by a vending machine at the train station. This type of open environment is what we call a society of digital systems. In this paper, we outline the characteristics of societies of digital systems, and argue that they call for a new approach to cope with unforeseen interactions, possible incompatibilities, failures, and emergent behaviors. We argue that designers can not assume a closed or homogeneous world, and must instead naturally accommodate dynamic adaptations. Furthermore, self-adaptability, that is, the ability to adapt autonomically to a changing environment, also poses problems, as different adaptation strategies may interfere negatively, leading to unstable behaviors. As...