This paper presents a context management system for supporting context-aware applications in a smart home. In a ubiquitous computing environment context changes dynamically and the applications have to adapt their behaviors according to the context. Therefore a contextaware system in a ubiquitous computing environment has to manage their context information effectively and satisfy qualities of context information required by contextaware applications. To solve these design issues we suggest a context-management system based on context metadata ontology. We defined context metadata ontology as the additional characteristics of context information to improve certainty, freshness, and understanding of the context information. Using the context metadata ontology, we have achieved effective context management. Our system also provides semantic-level interoperability between system components, because it is based on the ontology and service-oriented architecture. In this paper we explain co...