To provide the user with most benefits and personalized services using the available computing resources in ad-hoc networks, context-aware applications need to assimilate both the accessed and derived context information in the network. Derived context is inherently dependent upon sensed data or/and other context information. Context dependency may get introduced in a system due to various reasons, but as the number of context dependencies for an application increases, the more complex the process becomes to develop and maintain such an application. Due to highly dynamic nature of mobile agents in an ad-hoc network, too many context dependencies can severely affect the performance of a context-aware application. Reducing context dependencies or providing alternative context sources is crucial for performance gains in context-aware applications. But before addressing the issues of context dependency, we reckon that a formal analysis of context dependencies is required to better understand the problem. It will be much easier to understand, develop and maintain a context application if we have knowledge of its context dependencies. So, we define in this paper a formal model of context dependencies in a pervasive environment