Fable
The bridge builder cannot stamp the final seal himself
White Mist City was going to build a new bridge. The bridge-building team produced beautiful blueprints, load-bearing calculations, and test stone blocks, proving the bridge could carry traffic. The city lord was very satisfied and prepared to open it immediately.
But the old ferryman asked several unwelcome questions: which year's water level was used for the rainy season, had the heaviest convoy been tested, how would the bridge deck be handled when it iced over, and who had checked the assumptions in the drawings.
The bridge-building team thought this was nitpicking. They said they had already tested it many times and made the report even thicker. But the thicker the report, the harder it was for anyone to judge which parts were evidence and which were merely the bridge builders believing in themselves.
The city lord once tried having the bridge-building team review one another internally. As a result, everyone was familiar with the same set of assumptions and was also eager to rush the work, so many boundary issues were skipped as low-probability cases.
After a bridge in a neighboring city collapsed, White Mist City changed its rules. Before a new bridge opens, inspectors who were not responsible for building it must independently review its purpose, data, assumptions, calculations, tests, limitations, and contingency plans.
The bridge inspector isn't there to prove the bridge-building team wrong. They rerun key tests, spot-check material sources, design extreme scenarios, and confirm which vehicles can't cross and in which weather traffic must be restricted.
The bridge-building team was nervous at first, but later found that validation made the bridge easier to trust. Approvers knew where the risks were, bridge keepers knew what to monitor, and when something went wrong they could judge whether it was an out-of-design scenario or maintenance failure.
The new bridge finally opened, but the notice was written very clearly: what is allowed, what is not allowed, how long until re-inspection, and which changes trigger re-validation. The city lord finally said that validation is not adding trouble for the bridge builders, but letting independent evidence go first before the bridge takes on public responsibility. Later, every time Bailan City built a new bridge, it first arranged a bridge inspection day. The builders were still responsible for building the bridge well, and the inspectors were responsible for exposing assumptions to wind, rain, heavy vehicles, and public responsibility. The bridge keepers also received a checklist: when to limit flow, when to close the bridge, and when to call the inspectors again. The results of validation entered daily management rather than being locked in a cabinet. What the public trusted was not slogans, but the evidence left by this independent review.