1. Product design software embodied in a computer-readable medium and, when executed using a computer system, operable to: enable a user to define a product design structure, the product design structure comprising a plurality of customer concerns, a plurality of physical properties associated with components of the product, and a plurality of relation models, each customer concern being associated with at least one physical property via at least one mathematical relationship defined in at least one of the relation models; enable the user to input a value associated with one or more of the physical properties; calculate, using one or more of the relation models, the effect of the inputted value associated with the one or more physical properties on one or more of the customer concerns; display the calculated effect on the one or more customer concerns to the user; and enable the user to adjust the value associated with one or more of the physical properties to create a desired effect on one or more of the customer concerns, and wherein the product design structure further comprises a target value and an allowed range of values associated with one or more of the customer concerns and/or one or more of the physical properties, and wherein the product design software is further operable to generate a target value and an allowed range of values for a customer concern and/or a physical property based on the target value and the allowed range of values associated with another customer concern and/or another physical property via one or more of the relation models.