In terms of representation scenarios, '''design knowledge''' can also be categorized into off-line and on-line knowledge. 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.<ref>W.H.Wood III, A.M. Agogino, Case based conceptual design information server for concurrent engineering, Computer-Aided Design 8 (5) (1996) 361–369.</ref> 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 have 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.{{Citation needed|date=September 2011}}
