This volume presents the results of research work performed within ESPRIT Project 322 "CAD Interfaces (CAD*I)". It describes the concept for a methodology and guidelines to extend geometric modelling systems by modelling functions for the design of technical products. These functions are based on providing more semantics and design operations. A two-level concept for extending geometric modelling functions is presented, and geometric associative functions and technical functions reflecting technical terms and technical form features are defined.