On paper, a records office writes on the folder itself: the reference, the office it came from, the date after which it may be destroyed. Scan the folder and that writing has nowhere left to go. Write it inside the file instead and something worse happens — the file quietly stops obeying the archiving rules it says it obeys, and the day somebody checks it, it comes back refused.
Every archiving rule knows a title and an author; a keep-until date belongs to you. So this file carries those entries and, beside each one, a description of it: what it is called, how it is to be read, who it is written for, what it means. That description is what a checker looks for first, and what it accepts information nobody but you invented on. The page prints the very same five entries as the record hidden inside — a reference, a department, a date in 2056, a classification and a sheet count — so what a person reads and what a machine reads cannot drift apart.
Nothing is left out and nothing is simplified: this is the program exactly as it runs, for the developer who uses this library. The third is the description itself: a plain list of what the page has to say, which is what the service is sent.
Read the Rust source Read the Python source Read the JSON source
The document is lighter than it was, and every page still looks exactly the same. See this document's row in the table of every example.
Three rulers — centimetres, inches and points — on a page that tells whatever prints it to put it out at exactly the size it was drawn, and to offer nothing else. Lay a tape measure on the printed sheet and you can check for yourself.
Two sittings bound into one file. Each page carries a record of its own — what it is, whose hand wrote it, the day it was written — the photograph on the second page carries one too, and each transcription is tied to the page it transcribes rather than to the file at large.
Every line of the note carries the order it was picked for, the article code and the shelf it came off, and prints none of them. The place where the driver signs carries the round and the van, and one beside the fold tick carries nothing but its own place.
Two pages carrying a copy of themselves that nobody sees: this is a heading, this is a table, and this is the order to read them in. Software reading the document aloud follows that instead of the order the marks were drawn in, and skips the running head. On the page, nothing looks any different.
A parts list whose first column is a picture rather than a word. Each picture carries the sentence somebody hears in its place, so nothing in the list is lost on a reader who cannot see it. On the page, the pictures are simply pictures.
The electronic invoice French law has required since September 2026: one file, a page a person reads and the same invoice inside it as XML. Nothing to reconcile afterwards, because there is only ever one invoice.