Context awareness is one of the key requirements for realizing the vision of ubiquitous computing. Formal representation of context information fosters interoperability, eases evolvability and maintainability of applications, and enables a number of reasoning services. The proposed formal models are mainly based on the emerging standards such as the Web Ontology Language (OWL). Reasoning with ontology based models of context, however, is inherently complex and is further complicated by the dynamism of the context data. In this paper, we advocate an incremental approach for reasoning about dynamic context data; so as to avoid redundant computations and alleviate the cost of reasoning from scratch. The continuity of contextual states and existence of long-lasting subscription queries further encourage this approach. We present the related work on reasoning with dynamic data and conclude that the efforts do not address the problem adequately and are not tailored for specific considerations of context aware systems.