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. For example, through battlefield simulations, the customer can determine the incremental value of another 5 kph of vehicle velocity, or another 20 km of range.
Cost is defined by manufacturing flows up through design to the customer.
A marketplace in these three spaces supports mapping in both directions among them. In addition, the historical record of the design marketplace can help to reconstruct the rationale behind design decisions, just as historical economists now use records of commodity prices to reconstruct details of economic history. A chief engineer for a product can use a market in characteristics to parallelize the work of design teams, enabling them to evaluate many more alternatives than is otherwise possible. A product's characteristics can be thought of as dimensions of a Cartesian space within which the product is defined. This action simultaneously reduces the amount of that characteristic available for use by designers and increases the funds in the system available to purchase other characteristics to compensate for the decrease in the given characteristic.