Design is an important engineering activity, arguably the most important, because it is the basis for developing new products. An effective design support system can enhance the design process, and thus improve the design product. A number of requirements make the development of a design support system a complex task; useful and directed assistance requires a representation of the design process to be kept in a computable form. The system should furthermore have the flexibility to provide support for exploration, evolution, cooperation, and integration. The described work addresses the above issues, and proposes solutions for their achievement using the exploration-based model of design of Smithers et al. and the hierarchical decision procedure of Douglas. It proposes a fundamentally new representation consisting of three interconnected networks for the design objectives, alternatives, and models respectively, and examines the behaviour or functionality they must provide. Expected benefits from this representation are maintenance of consistency during the design process; dependency-directed redesign or retrofit; reuse of parts of the artifact or the design methodology; enhanced documentation and explanation of the system’s actions or advice; representation of multiple points of veiw and their interactions; and eased verification, modification and maintenance of the design product.