Fable
The cartographer put the meaning into the same map
There was an old library in the city. The librarian had to answer many questions every day: who wanted to find a book on bridge repair, who wanted a manual on brewing, who wanted a poem about parting. The earliest method was simple: shelve by the first character of the title. Books with similar titles were placed together, and those with similar characters were also adjacent. But readers soon discovered that similar names did not mean similar content. A copy of 'Moonlight by the Bridge' was placed next to bridge engineering, and a copy of 'Brewing Tax Law' was placed in the wine recipe section.
Someone proposed putting more tags on each book. The administrator tagged them 'bridge,' 'wine,' 'poetry,' 'law.' This was a little better than sorting by title, but a new problem arose: a book might discuss trade, ports, taxation, and family feuds at the same time. The more tags were added, the messier the shelves became.
Later, a cartographer came to the city. Instead of continuing to invent labels, he had readers place a small copper pin on a large map after finishing a book. Books on bridge structures landed near the river channels and stone districts, books of farewell poetry near the post stations and autumn wind districts, and books on caravan taxation between the port, the ledgers, and the government offices.
At first everyone laughed at him: how can books be placed on a map? The cartographer said, a map is not a place for books, it is a place for 'meaning.' A book can have only one position on a shelf, but its meaning can sit near many similar meanings on a map.
One day, a craftsman came to ask: I don't remember the book title, only that it talks about 'how to reinforce a wooden bridge after it gets damp.' The administrator didn't flip through titles again or guess at tags, but instead found the brass pin on the map near where 'wood,' 'bridge,' 'damp,' and 'repair' intersected. Several truly relevant books were quickly found.
Another poet asked: is there a poem that feels similar to "hesitation on the eve of a long journey"? This time the map was useful too. Those poems did not share the same keyword, yet they landed on nearby hillsides, because the emotions and situations they expressed were close.
Later, the library first surveyed every new book: not just recording the title, but turning its meaning into a string of coordinates on a map. Readers' questions were also measured as coordinates. The closer the two sets of coordinates, the more likely they were related in meaning.
The librarian finally understood that real improvement is not about making the bookshelf better at reciting book titles, but about enabling the system to calculate the 'distance between meanings.' With this map, finding materials no longer relies only on literal matches, but on semantic similarity. Once, the librarian placed two books very close together, but a craftsman pointed out that one of them only mentioned a bridge in a poem and could not guide bridge repair. So the cartographer added purpose and scenario validation to the map: similar meaning is only a candidate; you also have to consider what problem the reader needs to solve. In this way, the map is no longer just a pretty scatter plot, but a workbench where the library finds near neighbors and then a human judges whether they can be adopted.