The heart of the MGED system is its editing features. The editing features are divided into two classes: object editing and solid editing. Object editing is designed to allow one to change the location, size, and orientation of an object. Recall that an object is defined as the basic data unit of the MGED system and includes both combinations and solids. In the case of a solid, one needs to change not only its location, size, and orientation, but also its ``shape''. Changing the shape of a solid means changing any of its individual parameters. Hence, solid editing is handled separately.