The emergence of new technologies and the proliferation of mobile and handheld devices have facilitated development of context-based services. Common examples include the location based services. However, the revelation of the context and static information gives rise to new and very complex privacy concerns in such services. In this paper, we propose a formal model to regulate the privacy level of information passed to the service provider without disrupting the quality of information required for service access. The framework takes on two forms based on the receiver of the request generalization task to a trusted party or local device. A formal attack model assumes different levels of knowledge by the attacker and demonstrates the relative concerns of static information over contexts.