# Sibling facets

**For any file `x.md`, other things said about it live beside it as
`x.<facet>.md`.**

> **A facet is owned by whoever wrote the facet, never by whoever wrote `x.md`.**

**That is the whole of it.** *It exists so that two parties can both write about
one document without either of them reconciling two versions of it.*

## What a convention using this must decide

**Three things, and it must say all three or its adopters will not know they had
a choice.**

- **What the facet is called.** *`notes`, `usages`, `gaps` — the name is the
  contract; a reader recognises the pair on sight.*
- **What fixes `x.md` while the facet exists.** *Something must, or the facet
  comes loose from what it is about.*
- **How the pair is released.** *There must be an answer. **A convention that
  does not say leaves its adopters stuck**, and they will not notice, because a
  question nobody asks looks like a question already answered.*

## Why the facet is never owned by the source's author

**Because the source may not be theirs to change.** *An adopted document belongs
to whoever published it; a facet beside it is the only place a reader has to put
what they think.*