Recent developments in computer science and networking technologies motivate new families of applications that are sensitive to user and ambient contexts. The objective is to offer adaptive services that can be personalized to users' needs within heterogeneous, complex and dynamic environments. This requires enhanced and generic solutions for context representation and retrieval as well as for the interactions between heterogeneous systems and components. In this paper, we propose a conceptual model and a software framework using ontologies to build semantic context databases. Contextual information is modeled and implemented using first order logic and OWL to promote expressiveness and interoperability. The different steps to build the framework are detailed. The approach is then applied to the heterogeneous wireless access networks' use case. Measurements and performance results are provided and discussed.