Journal of E-Technology Yehia ElRakaiby, Frederic Cuppens, Nora Cuppens-Boulahia 1 2 2011 http://www.dline.info/jet/fulltext/v2n1/4.pdf In this paper, we present a formal contextual security model for pervasive computing applications. This model is developed by addressing the required featurs such as - support of authorization and obligation policies, monitoring and dynamic revocation of access rights, support of personalized security rule contexts, and support of collaborative applications. Besides we design the model in a way to be logic-based. The mdoel is thus elegant as it enables the use of formal policy conflict and dynamic system analysis techniques.