Systems meant to prevent harm may sometimes act before everything is known. How such a system undoes an action may matter as much as how quickly it acts. Wikipedia's current-events portal for March 13, 2009, recorded that seven people arrested for threatening to destroy several buildings in Amsterdam are released.

Designing for Reversible Actions

The entry does not say why the seven were released, and no reason should be read into it. In general terms, though, where a possible risk is serious, people responsible for safety may feel they cannot wait for certainty before acting.

Acting early may only be defensible if there is also a way to check and, where needed, reverse what was done. Any system that weighs how bad an outcome could be against how likely it is may face that tension.

Building a Way Back

A release after an arrest can be read in more than one way, and the entry does not say which applies here. In general, a process that can never undo a decision may be more brittle than one that can.

For people who build complex systems, one possible lesson is to plan the way back as carefully as the alarm. If an automatic flag or a person's judgement stops a process, a clear path to review that decision and, where right, lift it may be worth designing in from the start.

Perhaps resilience depends less on perfect foresight than on the ability to change course when more is known.

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