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RE: 200 response as conclusive evidence of an information resource

From: Booth, David (HP Software - Boston) <dbooth@hp.com>
Date: Thu, 4 Dec 2008 22:23:06 +0000
To: Pat Hayes <phayes@ihmc.us>
CC: Jonathan Rees <jar@creativecommons.org>, "public-awwsw@w3.org" <public-awwsw@w3.org>
Message-ID: <CD2B872281385A439B98164F5351E6DD39C4804230@GVW1144EXB.americas.hpqcorp.net>

Hi Pat,

> From: Pat Hayes
>
> On Dec 3, 2008, at 10:32 PM, Booth, David (HP Software -
> Boston) wrote:
> [ . . . ]
> > If you relax (or adjust) the definition of
> > IR to be "things that can yield AWWW:Representations", and if
> > you agree that a 200 response *is* an AWWW:Representation,
> > then there is no way that a reasonable person could disagree
> > with the "200 => IR" rule: it is a tautology.
>
>
> No, its not. What is indeed necessarily true is that the
> thing that sent the 200 response is an IR (on interpretation
> (b)). But that doesn't imply that the URI that was used to
> access it must be interpreted as denoting it. And that is the
> burden of http-range-14, seems to me: if you get a 200
> response back from thingie X, then the URI that you used to
> access X must be interpreted as also denoting X. After all,
> even if you get a 300 response, the thing that sent it was
> the same kind of thing that might emit a 200 response, and
> your URI accessed it in the same way; but in that case, you
> don't say that the URI denotes it, is the key point.

Good catch.  I vaguely wondered whether I needed to cover that
point.  :)

AWWW section 2.2 says:
http://www.w3.org/TR/webarch/#p48
[[
[URI] is an agreement about how the Internet community allocates
names and associates them with the resources they identify.
. . . .  For example, the "http" URI scheme ([RFC2616]) uses
DNS and TCP-based HTTP servers for the purpose of identifier
allocation and resolution. As a result, identifiers such as
"http://example.com/somepath#someFrag" often take on meaning
through the community experience of performing an HTTP GET
request on the identifier and, if given a successful response,
interpreting the response as a representation of the identified
resource.
]]

Section 2.2 goes on to say: "Of course, a retrieval action
like GET is not the only way to obtain information about a
resource. One might also publish a document that purports to
define the meaning of a particular URI."  But nearly all of
the 24+ billion pages that are currently accessible on the web
( http://www.worldwidewebsize.com/ ) create the URI-to-page
association by emitting representations, as opposed to
issuing explicit proclamations saying "henceforth this URI
shall denote that information resource").  One might claim
that the association that is created is merely an association
for *accessing* the page rather than *denoting* the page, but
I don't think that line of argument is very plausible, because
any name that can be used to access something can also be used
to denote it, and because we have no other widely used mechanism
for creating a *denotation* association between URIs and pages.

So if anything I think the burden of httpRange-14 is the other
way around: A 200 response is already widely understood as
indicating that the URI leading to the 200 response denotes
the thing that yielded the response, but why should a 303 *not*
lead to that same conclusion?  This is the leap that semantic
web practitioners are being asked to swallow.

>
> > The definition of IR that I have been proposing is
> > simply a more mathematical way to capture the idea that an IR
> > is something that can yield a AWWW:Representation, by
> > modeling it as a function from (Time x Requests) to
> > AWWW:Representations.  It is not the only way to describe or
> > model this concept, but it does have the advantage of being
> > relatively crisp.
>
>
> And of being entirely consistent with the REST model in Roy's
> thesis, by the way.

Yes, good point.



David Booth, Ph.D.
HP Software
+1 617 629 8881 office  |  dbooth@hp.com
http://www.hp.com/go/software

Statements made herein represent the views of the author and do not necessarily represent the official views of HP unless explicitly so stated.
Received on Thursday, 4 December 2008 22:25:34 GMT

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