Ubiquitous computing involves applications that adapt their behavior to every changing physical, social, and computing environment. This can be realized through proper capturing, representation, management and reasoning of constantly changing context. In this work, we propose a hybrid approach to collaborative context management. It uses semantic ontology and relational schema. System scalability is addressed by heuristic based selective loading of relevant context data into the reasoner. We have also developed a collaborative platform that performs context-aware reasoning and decisions based on the context management model. A result from the preliminary test shows that ourmodel is scalable and the platform is domain independent.