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Re: ConNegging on Description Pages (was RE: Southampton Pub data as linked open data)

From: Peter Ansell <ansell.peter@gmail.com>
Date: Wed, 30 Jul 2008 18:32:05 +1000 (EST)
To: Tom Heath <Tom.Heath@talis.com>
Cc: public-lod@w3.org, semantic-web@w3.org
Message-ID: <5278659.281217406721892.JavaMail.peter@Macintosh-2.local>

I think the idea with content negotiation is that you operate on URI's that aren't obviously relative to a particular format as your examples are. If you had http://revyu.com/people/tom/about as a URI that people try to resolve then you either 303 redirect them based on the content negotiation header, or you simply return the appropriate content in the response without a redirect (both would of course with the interlinks you talk about). It doesn't make sense to operate CN on the format specific URI's, as the person obviously has chosen the format by that point and the format inside the URI should be respected IMO.

I am not a standard sem-web person because I prefer the second option of just returning the appropriate content in the first response which itself contains the format-specific references inside if they want to get to another representation. They will know based on the content-type header of the response which one actually was chosen by the server so they can perform the resolution from that point if they have to because their desired content was not returned by the server the first time.



----- Original Message -----
From: "Tom Heath" <Tom.Heath@talis.com>
To: "Kingsley Idehen" <kidehen@openlinksw.com>, "John Goodwin" <John.Goodwin@ordnancesurvey.co.uk>
Cc: public-lod@w3.org, semantic-web@w3.org
Sent: Wednesday, 30 July, 2008 6:19:11 PM GMT +10:00 Brisbane
Subject: ConNegging on Description Pages (was RE: Southampton Pub data as linked open data)

Hi Kingsley,

If I've understood you correctly, you're suggesting that the HTML
document about a pub should 303 to the RDF/XML document about the pub if
RDF/XML is requested, and vice versa. (please correct me if I've

Is conneging on description pages desirable? i.e. if I request
in my regular browser (e.g. vanilla Firefox), should I be redirected to
http://revyu.com/people/tom/about/html ?

I don't think so, for the simple reason that I might be a developer
wishing to study/debug the RDF.



P.S. Of course <link .../> tags in the HTML header and foaf:page triples
in the RDF are highly desirable, this question is just about conneg on
URIs of Info Resources.

> -----Original Message-----
> From: public-lod-request@w3.org 
> [mailto:public-lod-request@w3.org] On Behalf Of Kingsley Idehen
> Sent: 28 July 2008 16:47
> To: John Goodwin
> Cc: public-lod@w3.org; semantic-web@w3.org
> Subject: Re: Southampton Pub data as linked open data
> John,
> I am getting:
> curl -I -H "Accept: application/rdf+xml" 
> http://www.johngoodwin.me.uk/pubs/description/pub1
> HTTP/1.1 200 OK
> Date: Mon, 28 Jul 2008 15:25:49 GMT
> Server: Apache/2.2.8 (Unix) mod_ssl/2.2.8 OpenSSL/0.9.7a
> mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/
> Last-Modified: Sun, 27 Jul 2008 15:52:16 GMT
> ETag: "1a0322-6ba4-453036415cc00"
> Accept-Ranges: bytes
> Content-Length: 27556
> Content-Type: text/html
> I am requesting the RDF/XML representation of the information 
> resource in question via it's URI, but not getting a redirect 
> to the RDF representation at:
> <http://www.johngoodwin.me.uk/pubs/data/pub1> .
> You're 200 OK in it's current form throws off RDF User Agents 
> such as our RDF Browser [1] and Data Explore extension for 
> Firefox [2] which will do the following:
> 1. Ask for an RDF/XML representation via Content Negotiation 
> 2. If we don't locate an RDF information resource from step 
> 1;  we will scan for <link rel="relevant-predicate" .../>, 
> GRDDL, RDFa 3. Normalize 4. Expose RDF graph
> We don't expect a 200 OK for an RDF requests with the 
> resource in question being an HTML representation, so right 
> now, we never get to discover the RDF information resource.
> Solution: just 303 to the RDF information resource that 
> matches RDF representation request.
> Then I should see: http://tinyurl.com/5he54t by starting at: 
> http://www.johngoodwin.me.uk/pubs/description/pub1
> instead of what I see currently at: http://tinyurl.com/6lkuaj
> Links:
> 1. http://demo.openlinksw.com/rdfbrowser2
> 2. https://addons.mozilla.org/en-US/firefox/addon/8062
> -- 
> Regards,
> Kingsley Idehen	      Weblog: 
> http://www.openlinksw.com/blog/~kidehen
> President & CEO 
> OpenLink Software     Web: http://www.openlinksw.com
Received on Wednesday, 30 July 2008 08:32:48 UTC

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