One aspect of resiliency that you may want to add is spare capacity (in terms of space, or time, or energy or materials). Ken Boulding use to talk about what he called the squirrel principle. Apparently he use to sit around the collage campus and watch what squirrels do and for how long they do it (the life of a tenured professor). He found that for most of the year squirrels spent their days in apparently unproductive activities (basically running around playing). Only for a few weeks a year were the squirrels busy gathering food. He considered that this kind of slack is an essential characteristic of enduring systems. You need to have fat that you can cut in lean times, or spare capacity (or spare time) so you can take advantage of abundance. Systems that are over optimized or too efficient fail because circumstances around them change.

Jim, maybe spare capacity can be folded under redundancy?

Adam,
Yes, having spare capacity is related to redundancy (and also minimal footprint and flexibility) but I think by giving the idea its own category it focuses attention on some qualities of systems that could otherwise be neglected. For example ecological carrying capacity, if you take the squirrel principle seriously the ideal population should be significantly below what the environment can support at the present time.

You can call it The Over Optimization Trap, or Fat is Good, if you are fond of the Sub-genius you can call it the Importance of Slack, but regardless of what you call it I think the idea is important to resilient systems.

Good call, Jim. I was seeing it as being part of redundancy, but you're right -- it's worth calling out on its own. Thanks.