Fable
Only after the city ordinance was carved into movable type could it withstand revision, testing, and questioning
Yancheng's rules used to be written on notices. Every time tax rates, shipping schedules, or embargoed goods changed, the clerk would recopy them and post them at each dock. After automated ledger ships appeared, notices were no longer enough. The ledger ships needed to make immediate judgments before invoicing, releasing goods, and reviewing—they couldn't wait for boatmen to run and read the small print on the wall.
The clerk first bound the notices into a booklet for each dock to follow. As a result, different docks understood them differently, and the same batch of salt could pass at the east gate but was stopped at the west gate.
After a tax rate adjustment, the north dock failed to replace an old notice, and the account ship released goods under the old rules. The error was not large, but no one could say clearly which version of the rules should have been in effect at that moment.
In the city, important city ordinances were changed to movable type. Each rule had a number, version, example, and approval record; before changing the type, it was tested in a sandbox to see which ships would be affected.
Every judgment of the ledger ship read the movable-type version of the rules. If the result was abnormal, the clerk could point out which rule, which version, and which modification caused the change. Later, when a compliance inspection arrived, the clerk no longer hauled out a pile of notices. He showed the rule book, test records, approval chain and execution traces.
The first error happened in the middle of the night. The ledger boat released a batch of salt sacks according to the old notice, and only at dawn did they learn the ban had changed the night before. The clerk said he had posted the new paper; the boatman said the dock was too dark to see it. If rules only hang on the wall, they can't keep up with every judgment.
Later Salt City wrote the rules into executable decrees that the ledger ships could directly enforce. When a ship arrived, a ticket was issued, or goods passed through the warehouse, the decree would immediately check the date, cargo type, origin, and permissions; changing the rules no longer meant only changing a notice, but changing the same executable decree and having all docks sync. The words on the wall were for people to read; the rules in the ships were responsible for actually blocking actions. The clerk's job also became easier. In the past he had to guess which dock had or hadn't read the new notice; now he only maintained the same decree in one place and checked whether each ship executed it. Only when rules moved from paper into action did disputes decrease greatly.
Yancheng learned that if governance rules are to enter automated execution, they cannot just be scattered in documents. They must be executable, testable, version-controlled and subject to after-the-fact review.