Recently, Sime has been curating a reading list on complex systems for the Test team book club at Linguamatics. The last couple of papers we looked at were Keeping It Too Simple by Paul J. Feltovich, Robert R. Hoffman, David Woods, and Axel Roesler and How Complex Systems Fail by Richard Cook.
Last week he suggested we stay with Cook but watch one of his talks, Resilience In Complex Adaptive Systems. The core concept from it is that systems operate in a space constrained by three boundaries: economic, effort, and performance.
Crossing a boundary causes some kind of failure, and there are pressures to keep the system away from them. Typically for economic and effort boundaries, it's management pressure with an eye on the bottom line.
However, continued management pressure coupled with accident-free periods will always tend to move the operating point towards, and even past, the margin: "We haven't had an accident recently, perhaps we're being too cautious. Let's use that spare capacity..." This is called flirting with the margin.
I sketchnoted the talk and, because I didn't do a great job, but found the visual model Cook described extremely appealing, I've broken with tradition and redrawn it for here.