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RE: Inference rules for HTTP, etc.

From: Booth, David (HP Software - Boston) <dbooth@hp.com>
Date: Fri, 29 Feb 2008 05:44:01 +0000
To: Tim Berners-Lee <timbl@w3.org>
CC: "public-awwsw@w3.org" <public-awwsw@w3.org>
Message-ID: <184112FE564ADF4F8F9C3FA01AE50009E254DB1237@G1W0486.americas.hpqcorp.net>

Hi Tim,

I spent a little time thinking about one of your major comments:

> From: Tim Berners-Lee [mailto:timbl@w3.org]
> Comments on the rules:
> http://esw.w3.org/topic/AwwswDboothsRules as of Mon Feb 25
> 09:06:15 EST 2008
> [ . . . ]
> ** Major.  You say:
> {
>          ?u1 a xsd:anyURI .                      # Old URI
>          ?r1 uri:hasURI ?u1 .
>          ?u2 a xsd:anyURI .                      # New URI
>          ?r2 uri:hasURI ?u2 .
>          ?u1 http:hasGetReply ?reply1 .          # IF ?u1 derefs to ?
> reply1
>          ?reply1 http:hasStatusCode "301"^^xsd:string .  # ... with
> 301 status
>          ?reply1 http:hasLocation ?u2 .          # ... and new URI ?u2
> } => {                                          # THEN they denote
>          ?r1 = ?r2 .                             # ... the same thing.
>          } .
> I don't think this is correct.   After much thought.   I think we need
> a "same work as".
> r1 and r2 can be for example the current front page of the NYTimes and
> a permalink (as they say)  for the same page.  If you assert =
> (owl:sameAs) then anything which applie to one applies to the other.
> This includes for example ?r1 uri:hasURI ?u2 for example.

Right.  I don't see any problem with that assertion.

It sounds like you are suggesting that the URI needs to be an inextricable part of the awww:InformationResource.  That's an idea that I floated at the WWW2006 Workshop in Edinburgh on resource identity, and the response in the room was uniformly negative:

I have been assuming that a an awww:InformationResource is independent of URI.  Thus a GET performed on URI ?u1 may yield an entirely different representation than a GET performed on ?u2 even though

        ?r1 uri:hasURI ?u1 .
        ?r2 uri:hasURI ?u2 .
        ?r1 owl:sameAs ?r2 .

> I think it
> includes a lot of things one would expect to be the same, like access
> control and copyright and authorship etc .. so "Same Work As" is
> useful.  But other things are not the same   ?r1 and ?r2  may be
> content negotiated, so one is more generic than the other, for
> example, as some people to conneg on a redirect.   So some of
> the http://www.w3.org/2006/gen/ont#
>   ontology may apply between them.

Hmm, that ontology seems to have useful concepts.  I should think about how to make use of them.  Thus far my HTTP ontology has said very little about awww:InformationResources.  It has modeled HTTP operations in terms of URIs.

> Because of the possibility of conneg, it is tricky to deduce many
> things.
> The tabulator at the moment classes as a TextDocument anything which
> has any http:getReply (through 301, 303, 307) of content-type text/.
> and similarly for image/* assumes it is a foaf:Image.  This results in
> a different user interface , and a different icon.
> You say, pointing to some issues, that "This helps explain why these
> HTTP rules are written in
> # terms of URIs rather than awww:InformationResources."  Indeed.  You
> do have to talk about URIs for these rules.  But most of the data
> about the resources will not. And the axiom
> { ?x = ?y.  ?x ?p ?z } =>  { ?y ?p ?z }  is too strong for things
> connected by indirection.

I think this is a good question.  I modeled 301, 302 and 307 redirects as indicating that the two awww:InformationResources are owl:sameAs largely because of the HTTP definitions of those status codes:

For 301:
"The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs."

For 302:
"The requested resource resides temporarily under a different URI."

For 307:
"The requested resource resides temporarily under a different URI."

Those all talk about "*the* requested resource", so it sounds to me like the new URI is denoting the same resource as the old URI in some way.

I'm not sure how a "Work" would be differ from an awww:InformationResource, or what utility class awww:InformationResource would have if we used a class Work.

David Booth, Ph.D.
HP Software
+1 617 629 8881 office  |  dbooth@hp.com

Opinions expressed herein are those of the author and do not represent the official views of HP unless explicitly stated otherwise.
Received on Friday, 29 February 2008 05:45:12 UTC

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