Abstract: For many complex and dynamic ubiquitous services, context-aware cooperation can be a solution. However, the way is not yet clear to make individual objects cooperate with each other as situations change. In addition, in the present environment in which many smart agents are already deployed, we are able to quickly develop ubiquitous services by utilizing existing agents. In the case of urgent but unavailable services, such fast development is required but there is no existing work to provide a path. To meet such requirements, in this paper, we thus introduce community computing as a new paradigm in which ubiquitous services are provided through context-aware cooperation among existing agents. To design such systems intuitively, we propose an abstraction model, called the situation-aware community computing model which includes the community situation model and the situation-aware cooperation model. In addition, for fast and convenient system development, we propose a development process based on the MDA (Model-Driven Architecture) approach [OMG, 03]. Following the development steps of MDA, we propose three models each having different abstraction levels and the model transformation process from the high-level model, CCM, to the source code. To make such transformation semi-automatic, we develop a toolkit, called CDTK. By using CDTK, we are able to implement a community computing system conveniently and systematically. To verify the proposed work, we implemented two small systems based on motivated scenarios; CHILDCARE and COEX-Mall. Through the simulated results of those systems, we examined the possibility of community computing as a new development paradigm.