Adaptive control systems designed to track dynamic goals are different than those designed to conform to static goals. Because product development has inherently high variability, it is critical to recognize situations where our goals should be dynamic. In such cases, we should strive to constantly reduce the gap between our current state and the economically optimal state, even when this economically optimal state is constantly changing. For example, this is commonly done in consumer marketing, where continuous preference-testing is used to detect market shifts that take place during development.
Donald G Reinertsen in The Principles of Product Development Flow