HM> Perhaps you, like Jonathon, are confused about the meaning
HM> of "name space" [...]

JdeBP> I'm using the definition of the term from RFC 1034
JdeBP> section 2.4.

HM> Again, I see your problem, the term namespace
HM> is not defined there -- the only use of the word
HM> is "namespace trees". In that reference it is only
HM> used as an "adjective" to "tree".

"name space" _is_ defined there. That's why it is in capital letters there.

HM> I am referring to SEPARATE namespaces

Different query classes aside (We are only talking about the "IN" class here.)
there is no such thing outside of "split horizon" DNS service. And even in
"split horizon" DNS service there is no concept akin to the one that you are
trying to propound - that of a single entity seeing multiple namespaces. A
single entity only ever sees _one_ (Internet class) domain namespace. The DNS
database content may comprise private and public content obtained from many
sources stiched together in a complex patchwork, but there's still just the
_one_ namespace for the owner names of the resource records.

You are putting forward a nonsense concept, and then saying that this nonsense
concept requires forwarding.