The vision leading the development of a Situational Awareness Knowledge Portal to support the Canadian National Defence Command Center in monitoring and directing Strategic-level Operations is to provide each individual with a customized, mission-oriented knowledge desktop that gives access to the right information from multiple sources in the context of the work and contributes to the building and sharing of the "collective battlespace knowledge". The approach lays on three intertwined fundamental concepts, namely Context, Ontology and Portfolio. The delimitation of the work into well-scoped portfolios allows, to a certain extent, to confine the knowledge handled. The exploitation of this knowledge using appropriate domain ontologies will make it feasible to provide contextual assistance in various ways to the work performed within portfolios, and accordingly to user/group preferences. This paper formalizes these concepts and their interrelationships.