Alternates header

[Lars Eilebrecht <La...@unix-ag.org>]

Hi,

I stumpled over a section in RFC 2068 which describes the 'Alternates'
header (content negotiation)...

 19.6.2.1 Alternates

   The Alternates response-header field has been proposed as a means for
   the origin server to inform the client about other available
   representations of the requested resource, along with their
   distinguishing attributes, and thus providing a more reliable means
   for a user agent to perform subsequent selection of another
   representation which better fits the desires of its user (described
   as agent-driven negotiation in section 12).

   The Alternates header field is orthogonal to the Vary header field in
   that both may coexist in a message without affecting the
   interpretation of the response or the available representations. It
   is expected that Alternates will provide a significant improvement
   over the server-driven negotiation provided by the Vary field for
   those resources that vary over common dimensions like type and
   language.

   The Alternates header field will be defined in a future
   specification.


mod_negotiation already has some code (network algorithm) to support this
header, but on what kind of requests does Apache output this header?
It seems that my tests always end up with 'na_not_applied' and I only
get a Vary header...

RFC 2068 doesn't impose any restrictions on the situations where
the Alternates header can or should be used, so I'm wondering why
Apache does not output this header for every negotiated resource.

Can someone shed some light on this?
Thanks in advance.  


ciao...
-- 
Lars Eilebrecht                     - DejaGNU: The strong feeling that there
sfx@unix-ag.org                    - is already a GNU-tool for your problem.
http://www.home.unix-ag.org/sfx/

Re: Alternates header

[Alexei Kosut <ak...@leland.Stanford.EDU>]

On Fri, 26 Jun 1998, Lars Eilebrecht wrote:

> I stumpled over a section in RFC 2068 which describes the 'Alternates'
> header (content negotiation)...

[...]

>    The Alternates header field will be defined in a future
>    specification.

[...]

> I'm wondering why
> Apache does not output this header for every negotiated resource.

So, um... what would this header contain, exactly?

I think if you #define TCN_02, Apache will generate the Alternates header,
in accordance with draft 2 of the transparent conneg spec. Which is, IIRC,
long since expired. I haven't kept up the the HTTP protocol groups, so I
don't know what the current state of content negotiation work is.

-- Alexei Kosut <ak...@stanford.edu> <http://www.stanford.edu/~akosut/>
   Stanford University, Class of 2001 * Apache <http://www.apache.org> *