Constraint management for collaborative design

Computer models for complex mechanical products are usually distributed among the various design team members using disparate software tools. Communication between these tools has previously been limited to occasional file transfer. Recent research has begun to provide support for dynamic models based upon communication between software applications. This work develops a methodology for representing and satisfying constraints in distributed product models to support collaborative design and concurrent engineering. The constraint management approach is based on propagation of specifications among constraints and design attributes. A hierarchical model for constraints and attributes allows design requirements to be expressed at several levels from simple geometric elements and variables to aggregate objects such as parts and sub-assemblies. Local reference objects provide an interface to aggregate objects outside a particular application. The propagation mechanism is based on message passing and therefore does not require a central constraint model. In addition, the mechanism supports a broad range of object and constraint types. A symbolic propagation methodology is also developed for solving coupled problems. The techniques are illustrated by the implementation of a distributed assembly design system