Context uncertainty and the incurred complexity of reasoning about context necessitate investigation of context awareness that would provide feasible solutions by means of models, architectures and algorithms. In this paper we discuss our approach for reasoning about context under uncertain conditions in pervasive environments and explore the theory, design and implementation of a reasoning engine, which makes use of a novel modeling approach for describing and reasoning about context. We discuss both a theory, which is the basis for the reasoning processes as well as analyze the functional activity of the reasoning engine during experimentation.