A significant amount of research has established that product platform planning is effective for the development of multiple products and management strategy for companies in today's market. However, there are still significant challenges in planning and the realization of product families and platforms. This is particularly true for determining family and platform architectures - imperative assets in companies in order to pursue competitive advantages. It is a challenging task because individual customization of products generally competes with the goal of maximizing platform commonality. To address this challenge, this paper introduces a graphical computer-based modeling environment to support product design teams in configuring modular product families. In the modeling environment, a product family can be decomposed into its products, modules, and functions. Also, interfaces among the product components can be elaborated by defining the relationship types (fundamental, redundant, and operational). Further elaboration can be achieved by defining an appropriate set of module drivers from four different perspectives: financial, customer, design processes, and organizational culture/IT. These features facilitate modeling of a product family at multiple levels of abstraction as capturing design drivers, reasoning and goals. The application of the modeling environment is illustrated with a family of coffee-makers. It is demonstrated how the proposed modeling method offers a comprehensive representation and understanding of product family planning by integrating multiple perspectives on modular architecting. Moreover, a matrix-based analysis option is provided for design teams to view the relationships between the technical functions and the forms, and the design goals and the customer requirements in a preliminary manner.