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D4P And D4F

As some of you may know, my friend Bill Livingston recently finished writing his latest book, “Design For Prevention” (D4P). While doodling and wasting time (if you hadn’t noticed, I like to waste time), I concocted an idea for supplementing the D4P with something called “Design For Function” (D4F). The figure below shows, via a state machine diagram, the proposed marriage of the two complementary processes.

After some kind of initial problem definition is formulated by the owner(s) of the problem, the requirements for a “future” socio-technical system whose purpose is to dissolve the problem are recorded and “somehow” awarded to an experienced problem solver in the domain of interest. Once this occurs, the project is kicked off (Whoo Hoo!) and the wheels start churning via entry into the D4F state. In this state, various structures of connected functions are conceived and investigated for fitness of purpose. This iterative process, which includes short-cycle-run-break-fix learning loops via both computer-based and mental simulations, separates the wheat from the chaff and yields an initial “best” design according to some predefined criteria. Of course, adding to the iterative effort is the fact that the requirements will start changing before the ink dries on the initial snapshot.

Once the initial design candidate is selected for further development, the sibling D4P state is entered for the first (but definitely not last) time. In this important but often neglected problem solving system sub-state, the problem solution system candidate is analyzed for failure modes and their attendant consequences. Additional monitoring and control functional structures are then conceived and integrated into the system design to prevent failures and mitigate those failures that can’t be prevented. The goal at this point is to make the system fault tolerant and robust to large, but low probability, external and internal disturbances. Again, iterative simulations are performed as reconnaissance trips into the future to evaluate system effectiveness and robustness before it gets deployed into its environment.

The figure below shows a dorky model of a system design before and after the D4P process has been executed. Notice the necessary added structural and behavioral complexity incorporated into the system as a result of recursively applying the D4P. Also note that the “Behavior Monitoring” structure(s), be they composed of people in a social system or computers in an automated system, or most likely both, need to have an understanding of the primary system goal seeking functions in order to effectively issue damage prevention and mitigation instructions to the various system elements. Also note that these instructions need not only be logically correct, they need to be timely for them to be effective. If the time lag between real-time problem sensing and control actuating is too great (which happens repeatedly and frequently in huge multi-layered command and control hierarchies that don’t have or want an understanding of what goes on down in the dirty boiler room), then the internal/external damage caused by the system can be as devastating as a cheaper, less complex system operating with no damage prevention capability at all.

So what do you think? Is this D4F + D4P process viable? A bunch of useless baloney?

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  1. March 23, 2013 at 4:30 am
  2. September 22, 2018 at 11:31 am

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