In recent years, there has been much research on ubiquitous computing, including context aware computing that is an important field in ubiquitous computing. The primary focus of this paper is on context modeling. We study the characteristics of context and so the requirements on the modeling. Besides, we also take into account the development requirements of next generation context-aware application. We study the context modeling approaches of some famous existing projects and find that few models meet all these requirements. In this paper, we propose a comprehensive model, which meets these requirements. We implement this model in a middleware called Scudware.