Generated by luria index from the record’s frontmatter — built, not edited.
Nothing declares an invariant, so nothing is checked.
A relation asserts that two documents have something in common. Naming the field that should say what — invariant = "tags" on the relation, or on a chain that walks it — turns that assertion into something a report can check. It is opt-in because naming the commonality is often the relation’s whole job: two papers joined by extends have succession in common, and extends is where that is written. Where no other field repeats it, a check reading one would report every edge.