Fable
Two shops: one makes electrical boxes, one arranges switch sequences
There was an electrical box shop in town, specializing in installing electrical boxes for various workshops. The electrical box managed three-phase power, overload protection, leakage tripping, and electricity usage record books. The shop's master often said, you can plug any machine into the electrical box and it will run; whether it runs well is not my concern, but if it catches fire, I will definitely trip the breaker before the fuse burns out.
Next door there was another shop, the Order Lantern Shop, which solved not the problem of where electricity comes from, but the problem of the sequence in which machines start. They had lit lamps for the dye workshop for ten years: the first lamp lit, telling the workers the water was boiled; the second lamp lit, meaning the dye vat could be loaded; the third lamp went out, meaning the dye vat must be sealed. Each step was a fixed sequence, and one wrong step meant starting over.
The two families originally kept to themselves. Until one day, the spinning workshop hired both the electrical box shop and the sequence lamp shop at the same time. The spinning workshop needed the electrical box to provide stable power, and also needed the sequence lamp to define the four steps: startup, spinning, winding, and shutdown. The craftsmen from both shops met in the workshop. The spinning workshop manager looked at them and suddenly asked a question that should not have been asked: which of you two is responsible for keeping the machine from making mistakes?
The electrician shook his head and said, my job is to pull the switch to prevent fires—but what a wrong spinning process is, I have no idea. The sequence-light technician also shook his head, saying I only handle whether the lights turn on and off in the right order—when the breaker suddenly trips, I neither know why it tripped nor how to restore the machine's previous state.
It took the steward a month to finally understand: he needed the underlying operating conditions the electrical box laid out for him—power supply, protection, and the record book; he also needed the business orchestration rules the sequence lights laid out for him—what to do first and what to do next. But between the two he was missing a layer: the steps set by the sequence lights needed the state snapshots and event notifications provided by the electrical box to correctly judge whether each step had actually been completed. Without this connecting layer, the light being on did not mean the machine had actually turned.
The two stores later cooperated to develop a public interface: each step of the sequence light sends a status confirmation request to the distribution box, and the sequence light advances to the next step only after the distribution box replies with the real-time machine status. The distribution box's overload protection was also connected to the sequence light's orchestration logic—if a machine overloads three times in a row, the sequence light's process automatically pauses and waits for manual inspection.
The spinning mill's year-end summary added a new budget line called orchestration and runtime interface governance. The manager said this money should have been approved on the very first day both parties entered the mill.