Re: [netmod] metadata in JSON

[Ladislav Lhotka <[e-mail]>]

Hi,

I would like to resolve the issue of metadata encoding in JSON, so let
me summarize the options we have. There are actually two valid questions:

1. Does the specification of the mapping of XML attributes in JSON
   belong to the yang-json document, and if so, in what form?

Possible answers:

1.1. No, as YANG doesn't model XML attributes.
1.2. Yes, as normative text.
1.3. Yes, as non-normative text.

For 1.2 and 1.3, we have to answer the second question because I assume
most XML attributes in use with YANG-modelled data will have non-null namespace:

2. How do we represent the namespace of an attribute in JSON?

Possible answers, using

  <elem xmlns:x="http://example.com/ns/URI" x:attr="foo">bar</elem>

as an example:

2.1. Use Clark's notation [1]:

  "elem": "bar",
  "@elem": {
    "{http://example.com/ns/URI}attr": "foo"
  }

2.2. Associate somehow every attribute with a YANG module, and then use
     the same notation as for encoding the namespace of YANG data nodes:

  "elem": "bar",
  "@elem": {
    "somemodule:attr": "foo"
  }

2.3. Associate somehow the XML namespace URI with a prefix in JSON and
     then use the same notation as for XML:

  "elem": "bar",
  "@elem": {
    "x:attr": "foo"
  }

In both 2.2 and 2.3, we need to say what "somehow" actually means. If we
accept 1.3, it could I guess involve a certain amount of hand-waving but
leaving it completely unanswered IMO makes the whole thing useless.

I personally think that 2.3 would be a step in a wrong direction because
the URI-prefix duality was recognized as a serious problem of XML
namespaces [2].

Please indicate your preferences or propose something else.

Thanks, Lada

[1] http://tools.ietf.org/html/draft-saintandre-json-namespaces-00
[2] http://blog.jclark.com/2010/01/xml-namespaces.html

Juergen Schoenwaelder <[e-mail]> writes:

> On Thu, Jul 31, 2014 at 10:49:07AM +0200, Ladislav Lhotka wrote:
>> 
>> On 31 Jul 2014, at 07:52, Juergen Schoenwaelder <[e-mail]> wrote:
>> 
>> > On Wed, Jul 30, 2014 at 05:53:30PM +0200, Ladislav Lhotka wrote:
>> >> 
>> >>>>> understand that this makes the solution somewhat incomplete but it
>> >>>>> allows us to finish this document now and to move forward.
>> >>>> 
>> >>>> That is my priority, too.
>> >>> 
>> >>> Good. So what speaks against saying that if attribute names clash and
>> >>> if attributes are scoped by a module name, then the encoding is XYZ?
>> >> 
>> >> I thought YANG 1.1 was a good opportunity to decide about how to do this scoping, provided that standard attributes are really needed.
>> >> 
>> > 
>> > Lets keep the discussion focused on the JSON document. Are you OK with
>> > the proposal to add text that attribute names may be scoped?
>> 
>> Yes, if there is no other choice. It is unclear what “scoped” means.
>> 
>
> Scoped by a namespace, such as 'namespace:identifier'.
>
> /js
>
> -- 
> Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> Phone: [phone]         Campus Ring 1, 28759 Bremen, Germany
> Fax:   [phone]         <http://www.jacobs-university.de/>

-- 
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: E74E8C0C