the system should be parametric. This means that selecting dimensions will modify models. Other features that are dependent on the modifications will update appropriately.

For instance, in a parametric CAD, you can select a dimension to modify the diameter of a boss protruding from a molded part with a round circling the base of the boss where it intersects the part. The boss diameter will grow and the round will also move so that it is still located at the intersection of the boss and the part.