Inferring 3-dimensional constraints with DEVI

Constraints can be used to specify and maintain spatial relationships among objects in a geometric design. In the 3-D geometric design domain , the diversity of possible relationships among objects makes it diicult for the designer to specify useful or intended relationships in a productive and intuitive manner. We have built a constraint-based 3D geometric editor called DEVI that infers possible or intended relationships among objects of the design. DEVI's database of relationships between design primitives can be extended using a descriptive language which enables the developer to specify a set of rules made up of conditions , to be satissed, and inferences to be made. Each rule has two parts; the rst is a boolean condition wherein a certain situation is described; the second part is an instruction to the system to infer the speciied constraint (or set of constraints) if the boolean condition is true.