Fable
The conveyor belt between the reading tower and the reply tower
When the Nan Commandery office handled letters from other places, it used to have the same group of people first read the files and then write the replies. When cases were few this was workable, but once cases increased, misreading and miswriting often blended together, and no one could tell where the problem was.
The prefect first asked everyone to write more detailed reading notes. The notes grew thicker, but the replies still went off topic, because the letter writers did not know which understanding results should be reviewed repeatedly.
Someone else pasted the entire incoming letter onto the reply desk. The clerk did see all the material, but had to flip through the whole scroll for every sentence written, slow as retrying a case from scratch.
Later the bureau split into two buildings: the reading building first organized input materials into a case representation, and the reply building then wrote while viewing the key representations left by the reading building via a conveyor belt.
The conveyor belt does not simply move the original text over; instead, at each generation step, it lets the reply building hall focus on the relevant parts of the input representation as needed.
This structure is especially suited to translation, summarization, question answering and converting one kind of input into another kind of output. Reading and writing are separated, making errors easier to locate: was it a misunderstanding, or a generation error. Later the steward wrote this lesson into the daily rules: first look at the scenario, then at the boundaries, and finally at who can take over when things fail. Only when all of this is clear does a beautiful demo become deliverable work.
The bureau later applied it to enterprise knowledge Q&A: first understand the client's materials, then output answers in the target format. Speed, quality, and controllability are all more stable than a messy free-for-all. The reading hall can't just leave behind pretty summaries either. It must retain enough structure: who made the request, where the key facts are, which evidence conflicts, and which parts can be repeatedly reviewed by the reply hall.
The prefect understood that complex transformation tasks need two rhythms: first fully understand the input, then produce output under control. If the bridge is well designed, reading and writing will not drag each other down. The reply tower is responsible for turning these representations into the target text. It does not re-read the entire scroll, nor can it freely improvise away from the conveyor belt. Once the two buildings had clear division of labor, the office had far fewer contradictions when handling long letters.