Re: [core] CBOR Encoding of Data Modeled with YANG

[Juergen Schoenwaelder <[e-mail]>]

On Tue, Dec 08, 2015 at 12:11:00PM +0100, Alexander Pelov wrote:
> Dear Juergen,
> 
> See inline.
> 
> > Le 8 déc. 2015 à 11:55, Juergen Schoenwaelder <[e-mail]> a écrit :
> > 
> > On Tue, Dec 08, 2015 at 11:16:58AM +0100, Alexander Pelov wrote:
> >> Dear Juergen,
> >> 
> >> The algorithm is straightforward - assign in increasing order a data 
> >> node ID to each element on the schema tree. If you have a revision of a 
> >> module, you do the diff between the old and the new tree, and add the 
> >> new data node IDs at the end of the numbering.
> > 
> > So I need access to the complete revision history in order to determine
> > data node IDs, correct?
> 
> It is not a must. You can manually indicate the node IDs of the newly added elements. If you want a completely automated allocation of IDs, then yes. The way I think this will work is - the publisher of a module will use the automatic tool to generate the statements, which will then be indicated in the YANG definition.
>

I want independently developed systems to interoperate. In general, I
can't assume modules have data node IDs (since a YANG module like lets
say ietf-interfaces simply does not define them).

> > What about imports without a revision (a nasty
> > source of ambiguity)?
> > 
> 
> There are two points in your question. The first is straightforward - Data node IDs make sense within the scope of a module. Changing a module does not affect the different modules which import it, with the possible exception of groupings, where the classical data node ID algorithm assignment kicks in (or manual ID assignment if the module author prefers so). In any case, I would refer you to RFC 6020, section 5.1.1. where the question of acceptability of imported modules is treated.

I am talking about imports _into_ a module that may be ambigous from
the viewpoint of the importing module. Section 5.1.1 is about import
by revision, my question was about what happens if there is an import
without revision. We had lengthy discussions in NETMOD what this means
for conformance and the outcome roughly is that this requires a
runtime lookup to find out which module revisions have been used by a
given implementation, that is, your algorithm would not only need the
complete revision history but also runtime information in order to
calculate unique data node ids.

There are alternate designs possible in the solution space. I like to
understand the trade-offs between them.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <http://www.jacobs-university.de/>