Integrating design process knowledge with CAD models

Abstract

Solid models are static entities, often defined by boundary representation models as sets of enclosing surfaces. Constructive Solid Geometry and feature-based computer-aided design environments create procedural descriptions of 3D objects in forms of history or CSG trees. These representations are temporally fixed, i.e., they describe the state of an object at a point in time. This paper describes a method to represent and capture temporal evolution of solid models - what we call model process history. We define process history to be all states of a model - the search space of design process. This paper presents a representational formalism we call model process graphs (MPGs). We use MPGs to integrate a model's description with a model of temporal changes that occur during the design process. We believe that MPG representations can have valuable application for many design and manufacturing problems. The paper describes our preliminary results to use MPGs to (1) create a record of design process; (2) store process-based design rationale; (3) represent in-process shapes for machined artifacts. We anticipate that similar structures will find application in other design and manufacturing problems where important process knowledge is embodied by temporal changes occurring in model evolution.