Solid modeling caveat

Solid modeling provides great repeatability. Shapes are not described as shapes but rather by semantics such as the diameter and depth of a hole. A solid modeling application records every action so you can make updates, such as changing fillet radii or hole diameters, by modifying the semantic to the new desired value. The computer handles the rest, rebuilding the entire shape according to the recorded history. The problem is that it's often difficult to describe a shape by semantics alone, so you end up compromising to complete the design.


Source:
Brad Redmond, Director of Industrial Design Marketing, think3, Inc.