Many nanopublications introduce something — a term, a role, a view — and give it a URI minted under the nanopublication's own address, recorded with npx:introduces. When such a nanopublication is superseded, the new version must keep that URI exactly, rather than mint a new one under its own address, so that everything referring to the thing keeps pointing at it.

The form does this automatically when opened in supersede mode. When writing a new version by hand, this is the one thing to get right: copy the introduced URI from the original, do not let it be regenerated.