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Re: Content negotiation: Why always redirect from non-information resource to information resource?

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Tue, 26 Jan 2010 19:11:37 -0500
Message-ID: <4B5F84B9.9020601@openlinksw.com>
To: Christoph LANGE <ch.lange@jacobs-university.de>
CC: Linked Data community <public-lod@w3.org>, Vyacheslav Zholudev <v.zholudev@jacobs-university.de>, Florian Rabe <f.rabe@jacobs-university.de>
Christoph LANGE wrote:
> Dear all,
>   in the well-known guides on cool URIs and publishing linked data, there is
> one thing I don't understand.  When doing 303 redirects, there are always
> three URIs/URLs involved:
> * U, the URI of the non-information resource (redirects depending on requested
>   MIME type)
> * U_R, the URL of the RDF information resource
> * U_H, the URL of the HTML information resource
> I do understand that it makes sense to have separate URLs for U_R and U_H.
> Delivering everything, be it RDF or HTML, directly from U (which would
> technically be possible) would impair cacheability.
> But why can't we do without U_R and do it like this?
> * If RDF is requested from U, it is directly served from U
> * If HTML is requested from U, a 303 redirect to U_H is made.
> I'd be interested in justifications for the above-mentioned best practice
> (with 3 URIs/URLs) that are based on semantic considerations and on HTTP
> architecture.  Restrictions imposed by Apache's standard plugins are not
> relevant to me.
> Cheers, and thanks in advance,
> Christoph

303 is a RESTful mechanism for disambigutating a Resource Identifier 
from the Address of and Information Resource (AWWW parlance). In 
distributed object technology parlance, this is about distinguishing an 
Object Identifier from the address of the network addressable Resource 
(a physical artifact e.g. document) holding its description (metadata). 
When you use Generic HTTP URIs for Object IDs you have to cater for the 
duality of this URI form i.e.,  it embodies an Object Identifier (Name) 
and an Address (Location) (i.e., Identity/Access duality).

Back to 303, this condition arises when your HTTP Identifier is slash 
rather than # (hash) terminated.

Goal: bind an Object ID to its metadata via sophistication of URI 

As for the HTML part, this is about providing an HTML representation of 
the Object (Resource) metadata rather than being confined to a single 
representation. Note, these days RDF based resource descriptions are 
served up in quite a few representations: HTML, HTML + RDFa, N3/Turtle, 
JSON, RDF/XML, TriX, TriG etc..

Hope this helps.



Kingsley Idehen	      
President & CEO 
OpenLink Software     
Web: http://www.openlinksw.com
Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter: kidehen 
Received on Wednesday, 27 January 2010 00:12:07 UTC

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