The use of context as an input is one of the major characteristics of Ubiquitous Computing systems. This paper looks into the structural and the systematic features of context in Ubiquitous Computing environments and their possible influence on context computing and the design of context-aware applications. This paper gives a definition regarding an understanding of context and how it is derived at a systematic level. Context interaction is investigated by a consumer - producer schema that models the exchange of context among artefacts. Validity, relevance, reliability and context history are identified and discussed as relevant systematic attributes of context.