
142 Chapter Seven Bringing Programming by Demonstration to CAD Users
conventional programming activity. Dimension-driven systems, or
parametrics for short, largely facilitate the design of part family models. For
collections or single shapes, just designing one shape provides for generat-
ing every family's shape.
7.2.3
Requirements for PBD in CAD
Most choices that have been made for our systems are governed by the do-
main area (CAD), especially users' habits and needs (particularly their ex-
plicit way for describing relations between objects), and by the goals of the
PLUS (Parts Library Usage and Supply) project, in which ...