Context as a service - Requirements, design and middleware support

Context-aware self-adaptive applications monitor and exploit knowledge about external operating conditions and adapt to changes in the execution context. Modern smartphones are equipped with several sensors, like GPS sensor or accelerometer. Additionally, context reasoners and external context providers exist. Thus, it is possible that several context providers offer information of the same type (e.g. location) but differ in quality levels (e.g. accuracy), representations (e.g. position represented in coordinates and as an address) and cost (e.g. battery consumption) for providing the information. In this paper, we provide a comprehensive approach and an according middleware architecture to support the selection and activation of dynamically appearing context providers according to specific context requests. Local context providers are activated dynamically on demand in order to save resources. Furthermore we provide support to overcome heterogeneous representations of dynamically discovered context information and their metadata.