The development of a collection of related products sharing a common platform represents an important approach in modern product design. An ongoing problem is the application of design methods toward a limited set of evolving product data and archived design knowledge to search and explore alternative platform options. With the goal of maximizing the reuse of end item artifacts and supply chain elements, we propose a design modeling method using basic qualitative relationships among relevant performance, design, and noise parameters in the system of interest. By using qualitative models related to multiple levels of design data, the method provides a single high level graphical representation among design data including archived knowledge in a design repository.