Context-Aware applications should consider the devices and networks engaged in the systems, as well as the complex control and data structures in the applications. This makes it not so straightforward to understand applications and to achieve the quality of applications, without well-defined formal model adequate to the intended goals. In this paper, we propose a formal model for context aware system, which provides device behaviors with temporal features, enriched with commonly used categorization of context. Thus this model enables integrated management of the interconnected devices with context information for a context-Aware system, so as to be employed for the critical purposes like safety enhancement. © 2013 IEEE.