Fable
Every merchant carries their own plug
The market of Fog Harbor was bustling. Salt sellers, cloth sellers, tea sellers, clock repairers and freight haulers set up stalls in the square every day. In the city stood a newly built dispatch tower, and the clerk inside was very clever: as long as he knew where goods were short, which road was blocked and which warehouse still had stock, he could arrange the whole city's business in perfect order.
The problem was that it was not easy for the clerk to learn these things. The salt merchant had his own ledger, the cloth merchant his own code, the tea merchant recorded inventory only with bamboo slips, and the clock repairer carved appointments on the back of a wooden board. For every merchant they took on, the dispatch house had to send someone to relearn a language, punch a new set of holes and wire up a new set of lines.
At first everyone thought this was just a nuisance, not a big problem. The dispatch tower said: important merchants first, others later. So the salt merchant was connected, the cloth merchant was connected, and the tea merchant barely got connected too. But a month later, the salt merchant changed the ledger format, the cloth merchant opened another warehouse, and the tea merchant switched to new bamboo slips. What the dispatch tower could read yesterday, it could no longer read today.
Worse still, the newly arrived carriage company also wanted to join. They asked: should we connect according to the salt merchant's line, or the cloth merchant's hole? The dispatch tower could not answer. Every old connection was like a hand-sewn patch—it looked usable, but could not be replicated.
The city lord brought in an old bridge builder. The bridge builder did not first study each merchant's ledger, but instead erected a bronze plate in the center of the square. Three things were engraved on the plate: first, whoever wants to provide a capability must register it in the same way; second, whoever wants to fetch data must request it in the same format; third, if anyone changes their own internal methods, as long as the bronze plate interface stays the same, the dispatch tower need not reconnect.
The merchants disliked it at first. They said, my ledger is special, my code words are flexible, my bamboo tallies are ancient. The bridge builder replied: how you keep records internally is your business; but if you want the dispatch tower to use them reliably, you must put a standard connector at the door.
Later, the salt merchant still used the salt merchant's ledger, the tea merchant still used bamboo slips, and the clock repairer did not throw away the wooden board. The change happened only between them and the dispatch building: each door had a small counter that could state what resources it had, what actions it could perform, what parameters it needed, and what results it would return.
From then on, new merchants joining no longer felt like rebuilding a bridge. The dispatch tower only had to look at the bronze plate rules to know how to connect; scribes no longer had to memorize each household's strange habits, but only request resources, tools, and context according to the standard. Fog Harbor City did not become monotonous because of this. On the contrary, the more different merchants connected, the more valuable the dispatch tower became. Because what was unified was not each person's inner world, but the door through which they handed their capabilities to others for use.