Abstract: To exchange synchronously geometric models among different commercial 3D-CAD systems through network,an XML-based description scheme of data with design intents is proposed.The scheme describes the construction processes of a geometric model in a hierarchical manner.The processes include the setting of the reference-planes,determination of the coordinates and constraints of the model primitives constituting profiles,and feature operations.Such a description scheme satisfies the needs of exchanging synchronously the design data with the design intents among heterogenous/homogenous CAD systems.