Design knowledge can be thought of as meta-knowledge and represents strategies for searching and exploring this space. Strategic knowledge is concerned with the decisions made during the conceptual design phase and is used for deciding the course of action when there are conflicting criteria. Strategic knowledge is used by the designer to decide what actions to perform in a given situation, where actions are considered to have observable consequences. Knowledge-based systems make control decisions at the implementation level. Strategic knowledge, by comparison, is defined at the knowledge level.
Substantive knowledge is used to describe or model the domain of endeavour.
It classifies entities in the knowledge base in terms of the relationships, attributes and functions between them. The procedure for deciding what to do when operating on the entities in the domain entities, is the strategy. Most of the current design support systems support mainly down-stream design. This process has not been supported very much by computer systems so far. In the connection, we must consider the problems of modelling ambiguity, tacit knowledge and so forth.