The general trend of computing is progressing towards the vision of ubiquitous computing, in which devices are seamlessly integrated into the life of everyday users, and services are readily available to users anywhere they go at any time. In contrast to the traditional computing paradigm, the ubiquitous computing environment is open and dynamic. Because of these characteristics, it is very important to understand how to use the general context concepts in the development of the context-aware system. In this paper, we propose the conceptual structure of context manipulation and describe how the context-aware system is developed based on this structure.