The product modeling has been one of the most important issues for the Computer Integrated Manufacturing systems. However, the design of the product model is very difficult since it must be adaptable to various phases of the design and manufacturing procedures. This paper provides the very basic consideration on the product model design to take the design procedure into account. The general arrangement design is used as an example in this paper. The design procedure was analyzed to derive the functionality of the product model. The product model must have both the conceptual structure and space definitions at once, and it was realized in the object-oriented product model with using the cross referencing between classes. Based on the consideration, the prototype system combining the three dimensional CAD framework and Object-Oriented Database was developed. The product model was illustrated by the trial general arrangement design on the prototype system.