[Cbor] CDDL use in DTN WG

[Brian Sipos <[e-mail]>]

Carsten,
Although there has been a good and consistent use of CBOR in the DTN WG,
the uptake of CDDL for documentation and implementation has been less
consistent. This may be due to its (perceived) complexity and maybe lack of
or maturity of tooling in the past. I was a heavy user of XML Schema and
all of the tooling that went along with it. I appreciate the current CDDL
and see how composition will help how existing definitions are able to be
used and how new ones can be steered to making their use easier.

For example, the definition Appendix B of RFC 9171 [1] makes use of both
sockets and generics to fully specify a protocol with many structural rules
and several extension points. The authors of RFC 9172 chose not to make an
explicit CDDL definition, but I constructed one [2] from the prose
explanations for my own validation needs and then extended that in a draft
[3] which also references rules from COSE RFC 8152 (which had to be
extracted from the source).

Besides a mechanism for composition, it would be useful to allow validation
tools to target a specific rule name as the required top-level item. I know
that this can currently be done by adding a new "first rule" in the
definition file but this is tedious and error prone when validating many
items against many possible top-level rules.

Let me know if any concepts or prototypes would be helpful to get feedback
on.
Brian S.

[1] https://www.rfc-editor.org/rfc/rfc9171.html#appendix-B
[2] https://github.com/BrianSipos/dtn-bpsec-cose/blob/main/bpsec.cddl
[3] https://www.ietf.org/archive/id/draft-bsipos-dtn-bpsec-cose-06.html