Stage 2 could not start without it. Three constraints already bound the shape
and between them they decide most of it.
JSON, because the standard library carries it and carries no YAML, and a YAML
declaration would put a third-party parser inside the one binary whose whole
argument is that it needs nothing — to gain authoring comfort in a document
generated by a machine and read by a machine.
An ordered list, because ordering is a DECISION. A host deriving order from
declared dependencies would be deciding the thing most likely to differ between
what the control plane intended and what the machine does. The control plane
knows what depends on what; it says so by saying when.
Unknown is refused, never skipped — an unknown version, type or field refuses
the whole declaration. A host that skipped what it did not understand would
apply most of a declaration and report success, which is 04-ISSUES/003 with the
declaration on the other side of the wire.
Complete for what the host OWNS, and only that. It removes what it previously
applied and is no longer declared, which it knows from the store rather than by
inference, and never removes what it did not create — a converger that treats
'not declared' as 'must not exist' deletes what the mesh never put there.
Two consequences arriving earlier than the build order suggested: the store is
load-bearing at stage 2, because nothing can be removed without knowing what was
applied. And a closed address space bounds the first vocabulary to what needs no
network, because a scenario has no route to a package repository.
