Re: [xmpp] <optional> and <required/>

[Peter Saint-Andre <[e-mail]>]

On 3/15/11 4:30 PM, Peter Saint-Andre wrote:
> On 3/13/11 12:54 PM, Waqas Hussain wrote:
>> On Wed, Mar 9, 2011 at 8:03 AM, Peter Saint-Andre <[e-mail]> wrote:
>>> On 3/8/11 7:47 PM, Kim Alvefur wrote:
>>>> Hi!
>>>>
>>>> Just to point out that these sections[1][2] seems to conflict with this
>>>> tread[3]. Otherwise, how does it make sense for roster versioning to be
>>>> required?
>>>>
>>>> [1]: http://tools.ietf.org/html/draft-ietf-xmpp-3920bis-22#section-4.9.3.23
>>>> [2]: http://tools.ietf.org/html/draft-ietf-xmpp-3921bis-20#section-2.6.1
>>>> [3]: http://www.ietf.org/mail-archive/web/xmpp/current/msg01125.html
>>>
>>> There are two different topics here:
>>>
>>> 1. Whether any given feature is mandatory-to-negotiate or
>>> voluntary-to-negotiate.
>>>
>>> 2. Whether to define a generalized mechanism for such signalling, which
>>> would apply to all features.
>>>
>>> The mailing list post you've cited applies to #2. Section 2.6.1 of
>>> 3921bis applies to #1.
>>>
>>> I see your point about the <unsupported-feature/> stream error: it might
>>> not make much sense to define such an error condition if there is no
>>> generalized mechanism for signalling that any given feature is
>>> mandatory-to-negotiate...
>>>
>>> Peter
>>>
>>
>> I think the <optional/> in 3921bis should go.
>>
>> 3921bis defines two stream features. Both are optional. One wants
>> <optional/> inside, the other doesn't. I think this <optional/> is a
>> leftover from when we tried having a generalized mechanism for
>> required features, and the only purpose it serves in this instance is
>> to add redundant inconsistency.
> 
> You might be correct. I will look at this during AUTH48, i.e., right now.

I've thought about this a bit more.

I agree that the <optional/> element here (copied from XEP-0237) is an
artifact of discussions ~12 months ago.

I would also assert that the roster versioning stream feature is merely
informative (as is true of the subscription pre-approval stream feature
in section 3.4), and that it would never be mandatory-to-negotiate.
Therefore I would prefer that we modify the text of Section 2.6.1 as
follows:

   If a server supports roster versioning, then it MUST advertise the
   following stream feature during stream negotiation:

      <ver xmlns='urn:xmpp:features:rosterver'/>

   The roster versioning stream feature is merely informative and
   therefore is never mandatory-to-negotiate.

(The latter sentence is copied from Section 3.4.)

Peter

-- 
Peter Saint-Andre
https://stpeter.im/