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Show is: 24 • Constraint satisfaction algorithms. The problem not addressed by previous work, and which is the foundation of this thesis How can model objects outside a particular modeling system's domain of constrainable objects be incorporated within the modeling system efficiently? Objects are considered to be outside the domain of oonstrainable objects when the derivation of the object using constraints is impractical or impossible. An exafll)le of an object outside the domain of constrainable objects might be a 8-spline curve or surface. Certainly, in the case of a 8-spline curve, the control points which define the curve are constrainable. However, it is impractical to derive the curve, for the purposes of intersection, display or tool path generation, using constraints. The solution to this problem. proposed by this thesis is a hybrid system using both constraint based model maintenance which may operate on constrainable objects, and dependency based model maintenance which may operate on all objects. |
