Design process knowledge can be categorized into ontologies. Off-line Knowledge Offline Knowledge refers to existing knowledge representation, including design knowledge in handbook and design ‘‘know-how’’, etc.; the latter refers to the new design knowledge created in the course of design activities by designers themselves. For the off-line knowledge, there are two representation approaches. One is to highly abstract and categorize existing knowledge including experiences into a series of design principles, rationales and constraints. TRIZ is a good instance of this approach. The other is to represent a collection of design knowledge into a certain case for description. Case-based design is an example of this approach. The key issue is on the computerization of the design knowledge representation. For instance, researchers at the Engineering Design Centre at Lancaster University, UK established a unique knowledge representation methodology and knowledge base vocabulary based on the theory of domains, design principles and computer modeling. They developed a software tool for engineering knowledge management. The tool provides an engineering system designer with the capability to search a knowledge base of past solutions, and other known technologies to explored viable alternatives for product design. On-line Knowledge On-line knowledge representation is capturing the dynamic design knowledge in a certain format for design re-use and archive. A few research efforts have been found in this area. Blessing proposes the process-based support system (PROSUS) based on a model of the design process rather than the product. It uses a design matrix to represent the design process as a structured set of issues and activities. Together with the common product data model (CPDM), PROSUS supports the capture of all outputs of the design activity. Ontologies Ontologies are being used for product representation (e.g.). Research suggests that there is a need to provide computer support that will supply clear and complete design knowledge and also facilitate designer intervention and customization during the decision-making activities in the design process. For example, WebCADET is a design support system that uses distributed Web-based AI tools. It uses the AI as text approach, where knowledge-based systems (KBSs) can be seen as a medium to facilitate the communication of design knowledge between designers. The system can provide support for designers when searching for design knowledge. References Design