Subject: draft-snell-http-prefer: Preference-Applied

From: Ken Murchison <[email-masked]>
Date: Thu, 06 Jun 2013 14:44:44 -0400

All,

I know its a little late for this feedback, but I thought I'd bring it 
to the list anyways.

The members of the Calendar and Scheduling Consortium (CalConnect) are 
beginning to use the Prefer header fairly heavily based on 
http://tools.ietf.org/html/draft-murchison-webdav-prefer Atour latest 
interop testing session earlier this week, one of the CalDAV client 
authors noticed that the use of the Preference-Applied response header 
by a server is currently documented as a MAY in 
draft-snell-http-prefer.  The ensuing discussion in the room reached a 
consensus of "if a client can't rely on a server returning this response 
header if/when it applies one or more preferences, then its not very 
helpful".

I know that Preference-Applied was reintroduced after a previous 
CalConnect interop session, but I don't recall if the strength of the 
conformance language for Preference-Applied was discussed on the list.  
Was there a compelling reason behind making the use of 
Preference-Applied only a MAY for servers, or can this be changed into a 
SHOULD or MUST?  Or would we be better served adding such language to my 
WebDAV Prefer draft?

Obviously, a server can choose not to apply any client requested 
preferences, but is there a use-case for a server applying a preference 
and not wanting to tell the client that it did so?

Regards,
Ken

-- 
Kenneth Murchison
Principal Systems Software Engineer
Carnegie Mellon University

---

From: James M Snell <[email-masked]>
Date: Thu, 6 Jun 2013 11:52:16 -0700

The Preference Header spec has already completed the RFC process. The
Preference-Applied was a MAY because there's no significantly
compelling reason to make it a SHOULD or MUST in all cases... there
are simply many cases where it's just not needed. It's utility really
depends on the nature of the Preferences being used.

On Thu, Jun 6, 2013 at 11:44 AM, Ken Murchison <[email-masked]> wrote:
> All,
>
> I know its a little late for this feedback, but I thought I'd bring it to
> the list anyways.
>
> http://tools.ietf.org/html/draft-murchison-webdav-prefer   At our latest
> interop testing session earlier this week, one of the CalDAV client authors
> noticed that the use of the Preference-Applied response header by a server
> is currently documented as a MAY in draft-snell-http-prefer.  The ensuing
> discussion in the room reached a consensus of "if a client can't rely on a
> server returning this response header if/when it applies one or more
> preferences, then its not very helpful".
>
> I know that Preference-Applied was reintroduced after a previous CalConnect
> interop session, but I don't recall if the strength of the conformance
> language for Preference-Applied was discussed on the list.  Was there a
> compelling reason behind making the use of Preference-Applied only a MAY for
> servers, or can this be changed into a SHOULD or MUST?  Or would we be
> better served adding such language to my WebDAV Prefer draft?
>
> preferences, but is there a use-case for a server applying a preference and
> not wanting to tell the client that it did so?
>
> Regards,
> Ken
>
> --
> Kenneth Murchison