A geometric constraint management system in Oar

This paper presents a constraint management system to experiment constraint-based design for mechanical engineering applications. The design is object-oriented and constraint-oriented. A design process can be viewed as incrementally creating design objects and imposing constraints on them. The system provides a sketch model and a constraint model which are loosely-coupled so that a designer can evolve a design by evolving both models separately. This system architecture is more appropriate for interactive design than existing systems. We use Operational Transformation Planning (OTP) as an approach to satisfy a network of geometric constraints [2]. The approach is different primarily in its use of geometric reasoning for satisfaction planning. An OTP system automatically generates a sequence of operations to satisfy a network of constraints, based on its understanding of the higher-level semantics of constraints and the geometric implications of the operations. Our system is implemented using Oar, an object-oriented programming environment with symbolic reasoning capabilities.

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