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Re: Alternative to 303 response: Description-ID: header

From: Dan Brickley <danbri@danbri.org>
Date: Wed, 05 Dec 2007 20:51:34 +0000
Message-ID: <47570F56.7030006@danbri.org>
To: Tim Berners-Lee <timbl@w3.org>
CC: Ian Davis <lists@iandavis.com>, "Sean B. Palmer" <sean@miscoranda.com>, David Booth <dbooth@hp.com>, www-tag@w3.org

Tim Berners-Lee wrote:

> There is a major problem with this, though.   Content negotiation is 
> just for different encodings of the SAME document.
> You can content negotiate between PNG and JPG of the SAME picture.

And SVG. Even quite lossily vectorised SVG...

> Between text/plain and text/html of the SAME document.
> Between RDF/xml and N3 of the SAME data.
> 
> You cannot use conneg to return a completely different document, eg not 
> A but  metadata bout A.
> A and A' must carry exactly the same information, module an 'acceptable' 
> degree of degradation.
> 
> When people conneg between HTML and RDF, the HTML is generated from the 
> RDF. Else it is  a bug.

I don't believe you on this, sorry!

There's no webarch ordering of RDF over HTML any more than there is of 
PNG over JPG (or SVG). You're appealing to causal chains here, but I 
suspect the key point you're after is that both encodings stem from some 
common source. If I decide to generate my JPG from a PNG, or my PNG from 
a JPEG, or both from some hidden 3rd source, that's my right. But I 
think it's the "hidden 3rd source" (ie. the abstract "Work") that's the 
core idea here. You don't really mind if I generate the .rdf by 
extracting from HTML, or querying a private SQL store, do you? So long 
as they both have close enough information content that they can 
sensibly be considered to be imperfect renderings of the same (more or 
less fictional or at least hypothetical) "Work"?

cheers,

Dan
Received on Wednesday, 5 December 2007 20:53:45 GMT

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