Because of the progress of research in the area of knowledge engineering, we can now use computers as intelligent machines, with many applications for expert systems. This paper describes a study of knowledge based systems that applies this progress to a computer aided design (CAD) systems for architectural planning and design. The constitution of building elements in Japanese wooden buildings is the subject of this study. Specifically, "Toko Waki", an ornamental recessed area found in Japanese drawing rooms, is chosen as a case study.

"Toko Waki" consists of many elements and has a specific system specifying the size, form, and proportion of each element. This modular system for Japanese wooden construction is called "Kiwari". "Shomei",one of the most famous texts of "Kiwari", has been handed down since Momoyama Era of sixteenth century. According to the "Kiwari" system,when the length of span is determined, the column dimensions are defined and then all other proportions of members are calculated successively.

The text of "Kiwari" is a specific knowledge of architectural design.On the other hand, people engaged in building construction have a general knowledge of the building process. These two observations lead to a conclusion that specific architectural knowledge is based on the general knowledge of the building process.

This study explores the general knowledge base for designing Japanese wooden buildings, and investigates the way that the knowledge of the constitution of building elements is represented.

This knowledge based system has a frame structure. It is composed of declarative knowledge representing the name and kind of frames, and procedural knowledge determining the size and position of each frame. In this study, each of the building elements, which are objects of complex form, are represented by rectangular prisms. This reduction of the complexity of building elements simplifies the data structure, and the abstract-specific inheritance of frames increases the efficiency of knowledge representation.

This paper also describes a linkage between a knowledge based system and a CAD system. With this linkage, the knowledge based system has only to define the size and position of each frame, and the CAD system handles presentations in two or three dimensional drawings. AUTOCAD is chosen as the CAD system in this case study.