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Re: Is 303 really necessary?

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Sat, 06 Nov 2010 19:08:13 -0400
Message-ID: <4CD5DFDD.8040402@openlinksw.com>
To: David Booth <david@dbooth.org>
CC: Ian Davis <me@iandavis.com>, Linked Data community <public-lod@w3.org>
On 11/6/10 4:42 PM, David Booth wrote:
>>>> httpRange-14 requires that a URI with a 200 response MUST be an IR;
>                                                           ^^^^^^^
> Not quite.  The httpRange-14 decision says that the resource *is* an IR:
> http://lists.w3.org/Archives/Public/www-tag/2005Jun/0039
>>>>   a URI with a 303 MAY be a NIR.
>>>> Ian is (effectively) suggesting that a URI with a 200 response MAY
>>>> be an IR, in the sense that it is defeasibly taken to be an IR,
>>>> unless this is contradicted by a self-referring statement within
>>>> the RDF obtained from the URI.
> To be clear, Ian's toucan URI *does* identify an information resource,
> whether or not it *also* identifies a toucan:
>    $ curl -I 'http://iandavis.com/2010/303/toucan'
>    HTTP/1.1 200 OK
>    Date: Sat, 06 Nov 2010 20:05:57 GMT
>    Server: Apache/2.2.8 (Ubuntu) DAV/2 SVN/1.4.6 PHP/5.2.4-2ubuntu5.10
> with Suhosin-Patch mod_wsgi/1.3 Python/2.5.2
>    Content-Location: toucan.rdf
>    Vary: negotiate
>    TCN: choice
>    Last-Modified: Fri, 05 Nov 2010 09:24:27 GMT
>    ETag: "264186-403-4944ad745a8c0;4944ad754eb00"
>    Accept-Ranges: bytes
>    Content-Length: 1027
>    Content-Type: application/rdf+xml; qs=0.9
> Thus, Ian has created an ambiguity by returning a 200 response.  There
> is nothing fundamentally wrong with this, as ambiguity of resource
> identity is inescapable anyway, and we just have to learn to deal with
> it.  However, for those applications that need to distinguish between
> the toucan and its web page, Ian is effectively suggesting the
> *heuristic* that if the content served in the 200 response says that the
> URI identifies a toucan, then the app should ignore the fact that the
> URI also identifies a web page, and treat the URI as though it *only*
> identifies the toucan.

What about this:

1. a 200 OK response infers that a URI is a URL (an Address) since its 
an indication of that a Resource has been located

2. existence of a self-describing resource discovered via 
"Content-Location" header value (e.g. touscan.rdf) can result in an 
override if the data states that the URI is a Name.

I really think we have to emphasize the "Address" and "Name" aspects of 
a generic URI, at every opportunity. Personally, I think it helps 
understand what the actual ambiguity is about.

This option showcases good RDF dog-fooding, especially as the Semantic 
Web Project has always been about self-describing data :-)



Kingsley Idehen	
President&  CEO
OpenLink Software
Web: http://www.openlinksw.com
Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter/Identi.ca: kidehen
Received on Saturday, 6 November 2010 23:08:44 UTC

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