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Re: Is 303 really necessary?

From: Norman Gray <norman@astro.gla.ac.uk>
Date: Sat, 6 Nov 2010 22:45:47 +0000
Cc: Ian Davis <me@iandavis.com>, Linked Data community <public-lod@w3.org>
Message-Id: <F6E6C2CF-8F71-4BDF-8CDF-3CBB52937CC3@astro.gla.ac.uk>
To: David Booth <david@dbooth.org>

David, hello.

On 2010 Nov 6, at 20:42, 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 

Yes, when I phrased this, I did indeed mean it as an analytic-must rather than an rfc2119-synthetic-must (this is the distinction you're making, yes?)

>>>> 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:

Indeed, because the decision defines what an IR is, so that Ian's toucan is necessarily an IR in the sense in which that term is currently defined.

> Thus, Ian has created an ambiguity by returning a 200 response.

(Ian can of course speak for himself, but...)

I take it that Ian is suggesting resolving the ambiguity he has created, and thus the need for any heuristics, by extending the notion of IR in such a way that a URI with a 200 response *is* an IR, *unless* dereferencing it returns RDF which (authoritatively) declares that the URI is a NIR.

> 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.

The suggestion does mean that the toucan URI, since it now identifies a toucan, cannot also identify the toucan's webpage, which is therefore unnamed.  I don't know if that's a problem or not (maybe it is, if you want to be able to say "I got this information about the toucan called </toucan> from <X>").  If it's a problem, then perhaps the </toucan> URI could point towards a </toucan.rdf> URI which contains the same RDF as </toucan>, but which is still an IR.  Then </toucan.rdf> is the toucan's webpage.

Best wishes,


Norman Gray  :  http://nxg.me.uk
Received on Saturday, 6 November 2010 22:46:19 UTC

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