The current development of context-awareness has introduced various emerging research areas to reduce complexity in developing context aware applications by applying service-oriented approach in managing context and establish context service. The establishment of context service will enable context aware systems to access and utilize context from context providers without paying necessary attention on how context information are composed and managed. Frequent changes of available context providers with different context quality are common phenomena in mobile environment. Hence, dealing with quality of context is a very important issue to provide reliable services for context management in this environment. We have identified some key requirements to establish context service and propose a service-oriented framework to facilitate context management in mobile environment. Furthermore we show our approach to deal with problem in providing appropriate context based on its quality requirements and the preferences of the corresponding context request.