How Complex Systems Fail

Came across this paper by Richard I. Cook, MD recently. Yep, it's written by a medical doctor and has amazing parallels to software systems. Anyone involved with software, especially engineers, should give this paper a good read.

The main bullet points:

1) Complex systems are intrinsically hazardous systems.

2) Complex systems are heavily and successfully defended against failure.

3) Catastrophe requires multiple failures – single point failures are not enough.

4) Complex systems contain changing mixtures of failures latent within them.

5) Complex systems run in degraded mode.

6) Catastrophe is always just around the corner.

7) Post-accident attribution accident to a ‘root cause’ is fundamentally wrong.

8) Hindsight biases post-accident assessments of human performance.

9) Human operators have dual roles: as producers & as defenders against failure.

10) All practitioner actions are gambles.

11) Actions at the sharp end resolve all ambiguity.

12) Human practitioners are the adaptable element of complex systems.

13) Human expertise in complex systems is constantly changing

14) Change introduces new forms of failure.

15) Views of ‘cause’ limit the effectiveness of defenses against future events. 

16) Safety is a characteristic of systems and not of their components

17) People continuously create safety. 

18) Failure free operations require experience with failure.