[core] map (5), ordering vs YANG SID in ietf-core-yang-cbor

[Michael Richardson <[e-mail]>]

Hi. I was trying to generate some code to implement a YANG model in
CBOR using:
  https://tools.ietf.org/html/draft-ietf-core-yang-cbor-05#section-4.2

which quite clearly says that I'm to use a CBOR map type (5).  Except that
my understanding of SIDs is that they are deltas for the key part.
(My other problem is that I don't have a SID until the SID document
progresses, but I can use the experimental range for now)

In many languages for which there are easy to use CBOR bindings, ruby,
python, perl, js, java, the CBOR map translates to a hash or directionary.
So I wondered how I could do deltas on keys in such an unordered structure...

My reading of:
  https://tools.ietf.org/html/draft-ietf-core-yang-cbor-05#section-4.2
about type 5, and then I read:
  https://tools.ietf.org/html/rfc7049#section-3.7

which says:
   The CBOR data model for maps does not allow ascribing semantics to
   the order of the key/value pairs in the map representation.

so, it seems that the SID concept as described in ietf-core-yang-cbor can not
work using the map type!!!
At first I thought it was just a language binding issue; that I needed
ordered sets of some kind, but no... It violates the above property.

Solutions that I can imagine:
1) use an array of 2-element arrays (requires an extra byte for each inner
   array!)
2) use an array 2x the size, and let the application reconstruct things as a
   hash after taking in account the SID delta.
3) use one of the discussed point/multi-dimensional-array/etc. structures
   that I believe were presented at IETF99... I think draft-jroatch-cbor-tags
   was the document.

I think that I favour (2), as being the most expedient and easiest to implement.

--
Michael Richardson <[e-mail]>, Sandelman Software Works
 -= IPv6 IoT consulting =-