Main idea

A context file starts out taking in everything that arrives. Information about the building, the contractors, the works — and, mixed in with it, the instructions saying how to handle a shared surname, where to put the threshold between small and large debtors, how to recognize the same person under two names. It is all useful, it is all in the same place, and the file passes a thousand lines.

Yet these two contents are not of the same nature. One describes the building, the other describes the way of describing it: that is mixing the recipe in with the ingredients. A rule is written in cold blood and holds until you change it; the material is written as the emails come in and never stops growing. Keeping them together means the stable part gets reread every time the moving part swells, and that you can't modify one without going through the other.

A directives.md on one side, a context.md on the other: the separation doesn't solve the volume problem — the material keeps swelling — but it makes the rest possible. As long as the rules are drowned in what they govern, no later split can be laid out cleanly, because you can't tell what has to be duplicated in every piece and what has to stay unique.

Why it matters

This gives the first split to make, and it isn't the one you'd think. Faced with an oversized file, the reflex is to cut it by topic; extracting first what isn't the topic — the rules — costs little and spares you copying the same instructions into fifteen thematic files.

It also supplies a diagnostic question applicable to any working document shared with an agent: does this paragraph describe the domain, or the way of handling it?

Nuances and limits

The border isn't always clean. "Debtors under a hundred euros are tracked separately" is a processing rule that contains a fact about the building, and it will have to be revised at the same time as the fact.

And the separation adds a file to maintain: if the directives stop being reread, they go on being applied without anyone remembering why they exist.

Open questions

• Where do you put a rule that holds for only one thematic file — in the shared rules file, or next to the material it concerns?