In spite of the current lack of theories and methods to effectively support customer demands, there exists great potential to better serve collaborative design customers in open innovation through increased access and involvement. In order to generate high-quality demands, it is necessary to provide product usage information that is easy for customers to understand. Based on the premise that customers participate in collaborative design as designers, this paper describes contexts in which customers are involved in four aspects of demand: clients, products, environments, and tasks. An analysis is then made regarding the actual impact of demand factors on the realization of these contexts. By considering the relationship between demand factors and functional specification parameters of products, this paper surmises that the way customers apply products affects the functional combination and parametric variables of products. The paper furthermore considers the impact of customer demand factors on product functions, and obtains the functional collection of the products to be developed. Also taken into consideration is the need for customers to communicate with each other in order to negotiate the practical problems of certain products. After a formal analysis on customers' abstract behaviors of product usage, the paper establishes a dynamic relationship between demand factors and the products to be developed, assisting vendors to better understand customer demand in the process of collaborative design and the actual product development process. To conclude, the effectiveness of this method is demonstrated by example, using an improved design of a product called the escape hammer.