Middleware support for quality of context in pervasive context-aware systems

Middleware support for pervasive context-aware systems relieves context-aware applications from dealing with the complexity of context-specific operations such as context acquisition, aggregation, reasoning and distribution. The middleware decouples applications from the underlying heterogeneous context sensors, and offers advantages such as rapid development of context-aware applications and efficient usage of the context sensors. Context sensors have inherent limitations with respect to the quality of the context information they produce. Without breaking the decoupling, the middleware needs to explicitly model and quantify this Quality of Context in order to allow application to adapt their behavior based on the Quality of Context, for efficiency reasons and to enable Quality-of-Context-aware privacy policies. In this paper we identify and define five Quality-of-Context indicators for context-aware middleware, and discuss different alternatives for their quantification. These Quality-of-Context indicators are: precision, freshness, spatial resolution, temporal resolution and probability of correctness.