[Cbor] draft-ietf-cbor-tags-oid-00.txt

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Reading this (and having read an earlier version), I really like the
concept because I have a fondness for OIDs and think they should be used
to name everything.

But there is a welter of problems around being able to "factor" an OID
tag out of an array or map.

Abstractly, if one can factor, one should be able to factor the tag out
of any number of layers of structure.  The trouble with that is that it
makes decoding difficult, as the decoder needs to keep the application
of the tag in mind as it descends through structures.

It would seem consistent that other tags might be defined with this
behavior, in which case a decoder might need to keep several factored
tags in mind as it is descending through structures.

Comparing with other types, a homogeneous array of OIDs is very like a
homogeneous array of integers, for which we already have a mechanism for
one-dimensional arrays.  OID arrays could be handled similarly, although
things are more complex because OIDs don't have a fixed-length encoding.

What isn't parallel with previous mechanisms is factoring from *maps*.
And that's novel because the factored tag applies to the keys but not
the values.  The reason for that is a bit arbitrary, and seems to be
because that's convenient for encoding X.500 certificates.

Factoring seems to be hard to do; trying to make it semantically
consistent and aligned with possible future tags with similar behavor
seems to require complex behaviors in the decoder.  Though this proposal
saves about 10% in X.500 distinguished name encoding.  Then again, are
distinguished names ever used when they aren't paired with keys (which
are much longer)?

Dale