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Re: Question about the On Linking Alternative Representations TAG Finding

From: Richard Cyganiak <richard@cyganiak.de>
Date: Thu, 31 Jul 2008 17:43:12 +0100
Cc: seb@serialseb.com, www-tag@w3.org, kidehen@openlinksw.com, tthibodeau@openlinksw.com
Message-Id: <51C7C742-6207-495B-AEB4-CD666541B7EA@cyganiak.de>
To: "T.V Raman" <raman@google.com>

Raman,

My question was not at all about HTML vs. XHTML, Sebastien injected  
that angle into the thread in a somewhat unhelpful way. I'm not  
interested in hearing yet more people's opinions on the issue. I ask  
for clarification of a detail in the TAG finding because I'm not sure  
how to interpret the finding's intention.

Let's say I have

/resource      (generic information resource with HTML and JSON  
variants)
/resource.html (a HTML specific URI)
/resource.json (a JSON specific URI)

Now let's say I request /resource.json with an Accept header of  
"Accept: text/html". What should happen?

One opinion is that the JSON should be served anyway, because the URI  
identifies a specific variant.

Another opinion is that the HTML should be served, or redirected to,  
because that's what the client asked for and the server has it  
available.

(A third opinion is that 406 should be answered, as suggested by  
Sebastien.)

What I'm asking for is simply a clarification of the advice in the  
spec. Did you intend that there be content negotiation on the  
representation_i URIs?

Cheers,
Richard


On 31 Jul 2008, at 17:21, T.V Raman wrote:

>
>
> I'm a bit confused at this point by the question.
>
> Could you flesh out your example?
>
> HTML  is a particularly good example, depending on how much you
> know about your HTML  resource.
>
> Though there is much debate on this, in my experience,
> wel--formed  XHTML survives well when served either as text/html
> or application/xml+xhtml.
>
> So if you have a resource under your control whose  content you
> know is well-formed XHTML that you would rather serve as
> application/xml+xhtml, but you also know that many legacy agents
> only accept text/html
> In that case, you might definitely want to  check the accept
> header and serve the appropriate response.
>
> Sebastien Lambla writes:
>>> Is it ever appropriate to configure content negotiation on the
>>> *representation-specific URIs*? So, if someone requests the  
>>> specific  URI
>>> for representation_1, but the Accept header indicates a  
>>> preference  for
>>> representation_3, should content negotiation kick in and   
>>> representation_3
>>> be served instead?
>>
>> If your url is the representation-specific one, then the conneg  
>> would fail
>> if the content-type of /resource.html is text/html and the Accept:  
>> only
>> contains application/xhtml+xml, as the representation is not the  
>> resource
>> and the url you requested is the one of the representation, not the
>> resource. I would return a 406.
>>
>> I'd understand the reasoning as being that if you dereference / 
>> resource.html
>> and get a 200 you can assert it is a document, if you were to  
>> conneg to
>> another url from the specific url you loose that assertion as  
>> defined in
>> httpRange-14
>>
>> Sebastien Lambla
>
> -- 
> Best Regards,
> --raman
>
> Title:  Research Scientist
> Email:  raman@google.com
> WWW:    http://emacspeak.sf.net/raman/
> Google: tv+raman
> GTalk:  raman@google.com, tv.raman.tv@gmail.com
> PGP:    http://emacspeak.sf.net/raman/raman-almaden.asc
>
>
Received on Thursday, 31 July 2008 16:44:17 UTC

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