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RE: N3 rule for proposed Resource-Description header

From: Williams, Stuart (HP Labs, Bristol) <skw@hp.com>
Date: Fri, 4 Apr 2008 14:08:56 +0000
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>, "public-awwsw@w3.org" <public-awwsw@w3.org>
Message-ID: <9674EA156DA93A4F855379AABDA4A5C611CE5505C9@G5W0277.americas.hpqcorp.net>

Hello David,

> -----Original Message-----
> From: Booth, David (HP Software - Boston)
> Sent: 04 April 2008 14:16
> To: Williams, Stuart (HP Labs, Bristol); public-awwsw@w3.org
> Subject: RE: N3 rule for proposed Resource-Description header
>
> Hi Stuart,
>
> > From: Williams, Stuart (HP Labs, Bristol)
> > [ . . . ]
> > I see Link or Resource-Description as equally applicable on a
> > 303 response. I see your ruleset entails a hasDirectGetReply
> > (ie. a 200). Actually, I would see such header based
> > references (which indeed the Location: based reference is as
> > well) as all having equivalent standing of "core"ness  or
> > otherwise - they involve the same amount of
> > forethought/deliberation to deploy. Would also work nicely
> > with a HEAD request on an IR.
>
> Hmm, it hadn't occurred to me that one might want a
> Resource-Description header on a 303 response.  But, yes, I
> can see that that could be useful also, and could be treated
> as indicating ancillary assertions just as for a 200
> response.

Well... I could just as easily see them as being (if we must use the terms) "core" assertions. I do not see the reasoned basis on which a distinction (at least for header based references) is made. I could, maybe, accept an ancillary stance for descriptions that are some number of links away (possibly just >1) from a response message (headers or body) for the requested resource. But descriptions referenced directly from the response surely carry equal weight from the point of view of being what the authority for the name meant to say.

[BTW: i haven't checked, but it occurred to me that the rules that you have been drafting don't check that the formula taken as declarations have anything to say about the declared resource; also are they singular or conjunctive?]

> I could see this as being particularly useful in
> support of suggested practice P4:
> http://dbooth.org/2007/uri-decl/#p4
> "A URI declaration page should provide links to suggested
> ancillary assertions about the resources whose URIs are
> declared by that page."

I remain unconvinced about the necessity or utility of the core/ancillary distinction.

> If the URI owner has already published a URI declaration and
> doesn't want to change it to add links to suggested ancillary
> assertions, then a Resource-Description or Link header could
> be a good way to do it.

Not that I want to argue for the distinction, quite the opposite in fact (see Pat and John Cowan elsewhere on "There are no such things as Unicorns" :-)) a Link: or Resource-Description: would be a good way to associate "core" assertion with an information resource/200 response particularly in cases where it is not possible to add them to the corresponding resource representation.

> > In this case the irrefutabilty comes from it being a 200...
>
> Right, it's the 200 response that gives it irrefutability --
> not the presence of a Link or Resource-Description header.
>
> > whereas, the redirection/linked references are orthogonal to
> > that (though I don't know what a Location: present in a 200
> > would mean... hmmm...). That Link or Resource-Description is
> > present in the response to not make for an irrefutable claim
> > that the resource is an IR.
>
> I don't know what you mean.  That last sentence seems to be
> missing some words or something, as I cannot seem to parse
> it.  Can you explain?

Trying again:

        That "Link:" or "Resource-Description:" headers are present in the response
        does not make for an irrefutable claim that the resource is an IR.

which is how the para on which I was commenting came across to me (ie. attributing irrefutable claim to headers rather than response code).

> David Booth, Ph.D.
> HP Software
> +1 617 629 8881 office  |  dbooth@hp.com
> http://www.hp.com/go/software
>
> Opinions expressed herein are those of the author and do not
> represent the official views of HP unless explicitly stated otherwise.

Stuart
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Registered No: 690597 England
Received on Friday, 4 April 2008 14:13:01 GMT

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