Fable
The two administrators in the library: one manages deleting books, the other manages the number of shelf slots
The royal library had two administrators. Old Ma was in charge of the shelves — the library had fixed-size shelves, each with one thousand slots, and each slot could hold only one book. Old Qin was in charge of the catalog — every day memorials, county gazetteers and letters from all over piled up at the library entrance, and Old Qin had to mark the core passages in red on each document that came in, cut out irrelevant appendices, pleasantries and repeated content, and then hand it to Old Ma for shelving.
At first the library ran well. Old Ma shelved by grid, and Old Qin trimmed by content. Later the volume of documents sent from various places tripled, and no matter how fast Old Qin worked, he could not trim it all. Someone suggested adding bookshelves to the library—expanding each shelf from one thousand grids to three thousand. After the new shelves arrived, documents that Old Ma did not trim went straight onto the shelves, and the library was packed full. Old Qin, in turn, discovered that after the shelves were expanded, everyone paid even less attention to document quality, because with more space, there was less insistence on concision.
The real trouble appeared when searching the archives. With documents Old Qin had cut before, if you wanted to find the salt tax record for a certain county, you could flip to the corresponding passage and see it. After the shelves were expanded, the uncut originals piled up to a thousand entries, and the same document was mixed with pleasantries, family genealogies and irrelevant cross-county comparisons. When archivists searched with the same keywords, the results tripled, but the truly useful parts were still just those few passages.
The library later came up with a compromise. Old Ma insisted the shelves could not be expanded indefinitely — every expansion raised maintenance and retrieval costs, and a bigger shelf did not mean better retrieval. Old Qin insisted cuts could not be one-size-fits-all — some documents were highly interrelated, and cutting a passage could break contextual coherence. The two co-wrote a pruning manual: decide the pruning strategy by document type and retrieval scenario.
A young clerk asked a question: if the library could hold a million shelves, would trimming still be needed? Old Qin retorted, would you stuff all the pleasantries into a million shelves too? The other said no trimming was needed since there was enough space. Old Qin told him to find one salt tax record surrounded by a hundred pleasantries among a million records. The young man searched for a day and said that what used to be found in three records now required going through a hundred.
Later, a couplet was hung at the entrance of the book pavilion: window size is the bookshelf grid, pruning strategy is choosing which book goes in which grid. Expanding the bookshelf doesn't solve the problem of choosing books.
Before retiring, Old Qin wrote a passage in the manual: the shelf grid determines the maximum number that can be placed, and the trimming craft determines how much value goes in. The two constrain each other—too few grids, and no amount of good trimming can save it; grids large enough but no trimming is equivalent to making visitors fish a needle out of a pile of nonsense.