As I read the Hayes article I was reminded of a design process model developed by Paul Pangaro that can be found in Hugh Dubberly’s “How Do You Design.”


The only information that I have of this model is Dubberly’s brief description of it.

Goal-action-feedback loops
after Pangaro (2002)
Paul Pangaro describes feedback loops in terms of a goalaction-
effect-measurement cycle. In this model, a system
acts to accomplish a goal within its environment. The system
measures the effect its actions have on the environment and
compares the effect to its goal. Then the system looks for
errors and acts (or re-acts) to correct them. By repeating the
cycle, the system converges on a goal or maintains a steady
state. Feedback is the information loop fl owing from the system
through the environment and back into the system. (For
example, a boat pilot tacking to reach port or a thermostat
turning a heater on and then off.)
Designers follow this cycle. They have goals, act to accomplish
them, and measure their results to see if they meet their
goals—goal-action-feedback. We’ve seen several analogs of
this process—define-prototype-evaluate and design-buildtest.
(See pages 50-51.)
Feedback is a central subject of cybernetics, the science of
goal-directed systems. Cybernetics has much to teach us
about fundamental structures of design.

But, even with only this limited description I find this model compelling and it seems to me that this is a more useful framework than presented by Hayes. This may be in part due to my affinity for systems thinking. Even in it’s stark simplicity, the Pangaro model has all the lovely trappings of an intriguing system. Yes, I see some weaknesses. Yes, I would make a few tweaks. But, I suspect that these are more a reaction to Dubberly visual translation than to Pangaro’s intent. For example the loop should, in my opinion, begin where it ends. This adjustment would need to be accompanied by a change to the text at the end of the loop. As this stand now it would appear to be a “mission accomplished!” statement. I think softening this in someway that allows us to re-enter the loop and repeat. I also feel that “Measurement” should be accompanied or followed by “reflection.”

I love that this entrance is “through environment” forcing the designer to contextualize their work from the very beginning. I love that the notion of the “feedback loop” is central to the system. I love that it is goal driven — and in this I assume that the goal can be that of user, participant, designer or other stakeholder.