ABSTRACT
Engineers may well accomplish self-consistent design, but its outcome, the artifact, can never be perfect in operation. Neither humans working at the front end (e.g., operators, maintenance persons), nor humans working at the back end (e.g., administrators, regulators) are perfect. The system (i.e., the combination of artifact and humans with various responsibilities) therefore cannot be perfect. It is not only the variability of human performances but also the human propensity for pursuing perfection with prescriptive rules while ceaselessly trying to change the system for better, that makes the system incomplete and imperfect as the time passes by.
