The functional view drives most designs, since it distinguishes the disciplines in which engineers are trained and in support of which design tools are available. Conflicts arise when different teams disagree on the relation between the characteristics of their own functional pieces and the characteristics of the entire product. It is easy to represent how much a mechanism weighs or how much power it consumes, but there is seldom a disciplined way to trade off weight and power consumption against one another. The more characteristics are involved in a design compromise, the more difficult the trade-off becomes. The problem is the classic dilemma of multivariate optimization.
Analytical solutions are available only in specialized and limited niches.
The problem is compounded with distributed multi-company design teams. Agents, representing design stakeholders for each component, buy and sell units of these characteristics on a network-based market server that repeatedly identifies opportunities for trades, computes clearing prices, and completes transactions. In some cases, analytical models of the dependencies between characteristics may help designers estimate their relative costs, but even where such models are clumsy or nonexistent, prices set in the marketplace define the coupling among characteristics. Designers, who typically have responsibility for intermediate levels of the product tree, propagate the constraints from the top and bottom of the tree toward each other. Value is defined by the customer, starting in Requirements Space, and flows down to design and then to manufacturing.