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

Hi Michael,

SID deltas in maps are parent-referenced (and not sibling-referenced) for this reason.
Do you see anything that makes you think they are sibling-referenced?
That would indeed not work in maps.

(We discussed using one or more of your solutions for introducing “ordered maps”, but then it seemed parent-referenced was good enough.)

Grüße, Carsten

> On Aug 17, 2017, at 05:03, Michael Richardson <mcr+ietf@sandelman.ca> wrote:
> 
> 
> 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 <mcr+IETF@sandelman.ca>, Sandelman Software Works
> -= IPv6 IoT consulting =-
> 
> 
> 
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