Pervasive applications are involving more and more autonomous computing andcommunicating devices, augmented with the abilities of sensing and controllingthe logical / physical environment. To enable context-awareness for suchapplications, we are challenged by the intrinsic asynchrony among the contextcollecting devices. To this end, we introduce the predicate detection theoryand propose the Predicate-Detection-based Context-Awareness (PD-CA) framework,in which: a) logical time is used to explicitly cope with the asynchrony; b)specification of predicates enables the applications to express contextualproperties of their concerns; c) online and incremental predicate detectionalgorithms effectively enable context-awareness at runtime. Under the guidanceof the PD-CA framework, we present the design and implementation of the MIPAmiddleware, which shields the applications from the burden of processing theasynchronous contexts. We also demonstrate how PD-CA simplifies the developmentof context-aware applications. Experimental evaluations show the performance ofMIPA in supporting context-aware applications despite of the asynchrony.
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