User-centric dependability concepts for ubiquitous computing

Ubiquitous computing has the goal of enhancing computer use by making many computers available throughout the physical environment, and thus providing the technical and conceptual means for enabling anytime, anywhere, anyhow computing. The technical realization of this vision has become feasible owing to recent advances in miniaturization and embedded computing technologies, which enable the integration of diverse computing capabilities into manifold everyday objects and devices. The multitude and diversity of computerized entities that are part of ubiquitous computing systems imply a number of technical challenges. On one side, the differences in form factors, functionality, and technical capabilities result in a great level of diversity of hardware and software, and a distinct heterogeneity in capabilities. Further, ubiquitous computing systems in general are often highly decentralized, featuring an exceptionally high volatility of cooperative relationships and topologies due to mobility, spontaneous interaction, and wireless ad hoc communication on behalf of system components. On top of that, a particularly significant characteristic of ubiquitous computing is its unprecedented degree of user-centricity. Ubiquitous computing systems are no longer distinct entities separable from the human user, but instead explicitly designed to embrace and support people in everyday life settings and situations. In the face of the technical issues and the strong user-centricity, coping with the dependability of ubiquitous computing systems and infrastructures constitutes a crucial challenge, especially since these systems are set to pervade and reshape people’s everyday life environment and the way they complete their daily chores. The goal of this dissertation is to provide a systematic study of critical dependability challenges in the context of ubiquitous computing, with particular consideration of the needs of the end-user, which to this point in time has not been investigated deeply in the research community. In doing so, we focus on two fundamental areas of ubiquitous computing: human-computer interaction and context-aware computing. Dependability in the area of human-computer interaction so far mainly focused on the design and implementation of user interfaces. However, with the emergence of highly interactive ubiquitous computing environments, the user’s dependence on interface devices has been increasing significantly even in everyday life situations. This leads to a new, user-centric type of dependability threat: given that a user requires certain user interface devices to interact with or to control a surrounding ubiquitous computing environment on a daily basis, it has to be investigated how he or she can cope with the unanticipated unavailability of these devices. It is therefore important to ensure the physical availability of user interface devices in order to preserve the accessibility of personal data and device functionality required as part of the human-computer dialogue. A further fundamental challenge is dependable contextand location-aware com-