Re: [netconf] restconf collections

[Kent Watsen <[e-mail]>]

[Update: a spinoff team has formed and is working on two I-D’s]

One issue has come up, regarding the encoding when GET returns a list or leaf-leaf.

Generally, in RFC 8040, GET returns an instance of the targeted resource.  This continues to be possible with JSON, as the list/leaf-list is a JSON array, but no array-equivalent exists with XML.  

This is likely why Section 4.3 states "More than one element MUST NOT be returned for XML encoding”, though this statement never needed to be said, as there is no case where more than one element would be returned anyway!

This intent of this email is to discuss changing that statement in 4.3, that is, to allow more than one element to be returned for the XML encoding.

Following are what I hope the WG can agree on being valid responses:

===== JSON =====


 REQUEST

    GET /restconf/data/example-jukebox:jukebox/library/artist?where=<expr>
    Host: example.com
    Accept: application/yang-data+json


 RESPONSE-1 (list exists, but no matching content)

    HTTP/1.1 204 No Content
    Date: Thu, 26 Jan 2017 20:56:30 GMT
    Server: example-server


 RESPONSE-2 (matching content)

    HTTP/1.1 200 OK
    Date: Thu, 26 Jan 2017 20:56:30 GMT
    Server: example-server
    Content-Type: application/yang-data+json

    {
      "example-jukebox:artist”: [
        {
         “name”: "Foo Fighters”,
          “album”: {
            “name”: "One by One”,
            “year”: 2012
          }

        },
        {
          “name”: "Nick Cave and the Bad Seeds”,
          “album”: {
            “name”: "Tender Pre”,
            “year”: 1988
          }
        }
      ]
    }



===== XML =====


  REQUEST

    GET /restconf/data/example-jukebox:jukebox/library/artist?where=<expr>
    Host: example.com
    Accept: application/yang-data+xml


  RESPONSE-1 (list exists, but no matching content)

    HTTP/1.1 204 No Content
    Date: Thu, 26 Jan 2017 20:56:30 GMT
    Server: example-server


  RESPONSE-2 (matching content)

    HTTP/1.1 200 OK
    Date: Thu, 26 Jan 2017 20:56:30 GMT
    Server: example-server
    Content-Type: application/yang-data+xml

    <artist xmlns="https://example.com/ns/example-jukebox">
      <name>Foo Fighters</name>
      <album>
        <name>One by One</name>
        <year>2012</year>
      </album>
    </artist>
    <artist xmlns="https://example.com/ns/example-jukebox">
      <name>Nick Cave and the Bad Seeds</name>
      <album>
        <name>Tender Prey</name>
        <year>1988</year>
      </album>
    </artist>



Thoughts?  If no objection, we will proceed as per above.

PS: I am aware, of course, of the pseudo-parent element (“collection”) defined in in draft-ietf-netconf-restconf-collection.  The hope is to avoid needing to introduce a pseudo element, as the above seems simpler, more consistent, and without issues, other than requiring that statement in Section 4.3 to be rescinded.


K.