A design problem cannot be comprehensively stated because the design problem has a multidisciplinary nature and the design problem itself evolves as solutions are attempted by the designer. This paper proposes a prototype architectural design environment , which aims to integrate various application for designing a building. Within a n object-oriented design environment, a unified data model and a date management system have been implemented to seamlessly connect all application. The suggested unified data model organizes the structure of the design data to keep the design consistent throughout the design and construction process . By means of the unified data model, integrated CAAD systems could represent and exchange design information at a semantic level, i.e. the user s way of thinking, such as exchanging components and features of a building rather than graphical primitives. In consequence, the unified data model reduces the misunderstandings and communication problems among the multiple disciplines of architectural design.