Thursday, December 29, 2016

The requisite law of variety


Now, this could be a bit stuffy: "The Requisite Law of Variety"

But actually, it's an interesting concept to consider, to wit:
  • Essential Elements (E): these are outcomes, results, or other artifacts that you want to have some control over, even if you are Agile
  • Disturbances (D): these are events or actions that impact E .... usually there are a lot of these!
  • Regulation (R) or controls: these are the means or actions to limit the impact of D's. Even in the Agile world, there are some controls or protocols to regulate the pace and rhythm
  • Passive capacity (K): in effect, buffers and elasticity that limit the fragility of the system and allow for some absorption of D without breaking E 
The Law is a bit mystical when expressed as math, essentially saying:
"the the variety -- or set -- of the E's that you need control over should be greater than (1) the variety disturbances-reduced*-by-regulation and (2) further disturbances-reduced-by the buffers or elasticity."
* reduced, absorbed, or mitigated
Anthony Hodgson puts it this way:

[The Law of Variety] ... leads to the somewhat counterintuitive observation that the regulator must have a sufficiently large variety of actions in order to ensure a sufficiently small variety of outcomes in the essential variables E.

This principle has important implications for practical situations: since the variety of perturbations a system can potentially be confronted with is unlimited, we should always try maximize its internal variety (or diversity), so as to be optimally prepared for any foreseeable or unforeseeable contingency.

If you are familiar with the ideas of "anti-fragile" in system design, this last sentence is a good alternate phrasing for what makes systems anti-fragile, i.e. resilient


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