MOST CONVENTIONAL SOLID MODELING OR COMPUTER- AIDED DESIGN (CAD) SYSTEMS ARE INADEQUATE FOR MECHANICAL DESIGN. THIS IS DUE TO THE COMPLEXITY OF DESIGN MODIFICATION, DIFFICULTY OF MANIPULATION, AND LACK OF PRODUCT INFORMATION. IN A HIGH PRODUCTIVITY CAD (HPCAD) SYSTEM, THE USER IS ALLOWED TO FORM AND DEFINE THE DESIRED FEATURES BY USING A COMBINATION OF BOOLEAN CONSTRUCTIVE SOLID GEOMETRY (CSG) OPERATIONS (UNION, INTERSECTION, DIFFERENCE) ON A FAMILY OF POLYHEDRAL PRIMITIVES, FLEXIBLE SUPERQUADRICS, AND A VARIETY OF SURFACE REPRESENTATIVES. THIS PAPER DESCRIBES THE THEORY OF THIS GENERALIZED CSG (GCSG) PARADIGM AND FORM FEATURE MODELING SUPPORT.