Brian C. Williams
An inventor who is skilled at constructing innovative designs is distinguished, not just by the first principles he knows, but by the way he uses these principles and how he focusses the search for novel devices among an overwhelming space of possibilities. We propose that an appropriate focus for design is the network of qualitative interactions between quantities, (called an interaction topology), used by a device to achieve its desired behavior. We present an approach, called interaction-based invention, which views design as a process of building interaction topologies - in this paper directly from first principles. The program Ibis, which embodies this approach, designs simple hydro-mechanical regulators, analogous to devices that were fundamental to the development of feedback control theory.