This paper presents “ConServ1 ”, a web service for context management. ConServ allows smart spaces to access user’s context data according to user-defined policies. This web service addresses the sharing and management of context data between smart spaces and as a result facilitates the creation of new smart spaces and the enhancement of old ones. Data related to a user’s location, calendar, habits, relationships and privacy policy are combined to provide rich context data while users are provided with a single place where they can control the access of all smart spaces to their context data. ConServ provides a set of ontologies, which leverage existing popular ontologies, to model user’s context data and the interacting smart spaces.