SOLID MODELING WAS FIRST OFFERED COMMERCIALLY IN CAD/CAM SYSTEMS IN THE EARLY 1980S. SINCE ITS INTRODUCTION, HOWEVER, WE HAVE SEEN LIMITED USE OF SOLID MODELING TECHNOLOGY IN APPLICATIONS FOR WHICH IT HOLDS SO MUCH PROMISE. THIS PAPER LOOKS AT SOLID MODELING FROM AN APPLICATION PERSPECTIVE. IT BEGINS WITH A SHORT BACKGROUND OF EARLY SOLID MODELING SYSTEMS AND FOLLOWS WITH AN OVERVIEW OF PROBLEMS THAT APPLICATION DEVELOPERS HAVE ENCOUNTERED WITH EXISTING SOLID MODELING SYSTEMS. AN ARCHITECTURE FOR AN OPEN AND EXTENSIBLE GEOMETRIC MODELING SYSTEM IS THEN ANALYZED. SPECIFIC EXAMPLES DEMONSTRATE AN NC PROGRAMMING SYSTEM BASED ON SOLIDS