[Recipes] Puzzle with HTTP Accept, Firefox header plug-in and RDF

Hi everyone,

Related to getting the SKOS RDF file by it default URI (or at least to test that ability), I wanted to change my browser's headers so that it asks for RDF data and not HTML anymore.
Following Sean's advice, I have installed the ModifyHeader plug-in for Firefox (I'm still at version 2.0).

I now have the following problem.
I have changed the Accept header sent by my Firefox to application/rdf+xml (only)
On dbPedia, when it queries [1] , Firefox gets redirected to the RDF file [2]. Perfect!
But when it queries for the SKOS 2008 file [3], Firefox gets redirected to [4] and not to [5].

How come? What is puzzling is that Vapour [6] reports that everything is ok with both URIs [1] and [3], even though the behaviours differ when there is no content negociation. Interestingly, Vapour itself recognizes my Accept headers: when I activate the application/rdf+xml only, it sends its reports in RDF, while it sends the HTML if I do nothing.

Is there something more than Accept header involved? Has my plug-in bugs, or am I just too dumb to think of myself playing with that kind of stuff?

Thanks for any feedback,

Antoine


[1] http://dbpedia.org/resource/William_Shakespeare
[2] http://dbpedia.org/data/William_Shakespeare.rdf
[3] http://www.w3.org/2008/05/skos
[4] http://www.w3.org/TR/2008/WD-skos-reference-20080829/skos.html
[5] http://www.w3.org/TR/2008/WD-skos-reference-20080829/skos.rdf
[6] http://validator.linkeddata.org/

========================

http://www.w3.org/2008/05/skos

GET /2008/05/skos HTTP/1.1
Host: www.w3.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.8.1.20) Gecko/20081217 Firefox/2.0.0.20
Accept: application/rdf+xml
Accept-Language: fr,en-us;q=0.8,fr-fr;q=0.5,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive

HTTP/1.x 303 See Other
Date: Thu, 12 Feb 2009 15:13:21 GMT
Server: Apache/2
Location: http://www.w3.org/TR/2008/WD-skos-reference-20080829/skos.html
Cache-Control: max-age=21600
Expires: Thu, 12 Feb 2009 21:13:21 GMT
Content-Length: 269
Connection: close
Content-Type: text/html; charset=iso-8859-1

Received on Thursday, 12 February 2009 15:39:35 UTC