Actual CAD systems are still monolithic and are based on complex geometrical models. Moreover, they have complex computer-human interfaces which are an obstacle to the modelling task for a non-expert end-user. Our aim is to implement a new approach taking advantage of web possibilities and providing a novice end-user with an easy-to-use system. We are thus interested in providing a trade-oriented interface more intuitive than a classical one.

This paper deals with the implication of such an interface on the intrinsic architecture of CAD systems. We first introduce in this paper our modelling approach, called synthetic, which corresponds to an intuitive solid modelling method. We then present a multilevel architecture which allows the management of instructions from geometrical environment to application environment. We end with an application of this architecture to an operational system.