【正文】 cture tree (topology) is dynamic, so that KBE offers true engineering automation including application development, geometric modeling, application deployment and tools integration. Knowledgebased engineering is a programming tool used to develop a virtual prototype or a design advisor for the design of an established product in a given design domain. Dym, et al. [3] and Gonzalez, et al.[4] provide valuable overviews of KBE. Existing knowledge about a class of designs is utilized in knowledgebased engineering or design (KBE or KBD) and organized into a database format usable by puters. Detailed designs or virtual prototypes are then rapidly developed KnowledgeBased Engineering (KBE) Design Methodology 23 through the use of digital puting power, developed databases, and systems of rules. The product model which is developed in the KBE environment is a virtual prototype. A virtual prototype has all of the geometric characteristics or attributes of the product as well as the nongeometric attributes such as materials, mass properties, stress and deflection characteristics, etc. Once the virtual prototype is created, it can be used by the designers to evaluate the success or merit of the design configuration, and then modify it if desired. The product model represents the engineering intent behind a geometric design. The information contained in a product model includes physical attributes like geometry, material type and functional constrains. Generative technology There are three types of KBE tools that are currently being explored and developed. These include： 10 1. Diagnostic approach (expert system). 2. Creative approach (design advisor)/(design checking). 3. Generative approach (virtual prototype). The expert system was the first type of tool developed for use in the engineering tool is used for diagnostic purposes such as analyzing a malfunctioning automobile engine. The second type,design advisor,is the one to more current is used to follow the design process of a system, and advise the designer of constraint and rules violations based on rules contained with the design advisor. The designer then acts on this advice and makes appropriate changes. The third type involves developing a model of the system based on rules contained with the model. This model, a virtual prototype, then reacts to changes in attributes (either geometric or nongeometric), and regenerating a new instance of the prototype. This is the type of KBE that is used in the classes developed. KBE uses generative technology to capture generic product design information, including geometry and topology, product structure development and manufacturing processes as design rules. Generative modeling maps functional specifications to a detailed representation of the product. The advantage of a generative model is that as the product requirements change, the design representation is immediately updated directly affecting all outputs. Thus, KBE is a dynamic object model wherein the representation of the design is continually updated. KBE methodology facilities the capture of engineering and manufacturing knowledge into a generative model by rapidly generating new designs from functional specifications. In contrast to the conventional design tools, KBE offers true design automation vs. design assistance. KBE is a robust design technology for continuous redesign of a system during the design process. KBE product representation Current KBE software is based on an objectoriented nonprocedural design language such as LISP. As a result, the design information need not be ordered correctly within the model, as it will work out the order itself. Objectoriented programming works on the concept of