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Re: Confusion on httpRange-14 decision

From: Ralph R. Swick <swick@w3.org>
Date: Fri, 17 Feb 2006 10:05:08 -0500
Message-Id: <5.1.0.14.2.20060217075225.036c2c20@127.0.0.1>
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>
Cc: <public-swbp-wg@w3.org>

At 06:22 PM 2/15/2006 -0500, Booth, David (HP Software - Boston) wrote:

>Here is a draft message to the TAG, per my action item.  Comments?

looks good.  Some points below.

...
>WHAT IS THE CONFUSION?
>The httpRange-14 decision says that if an HTTP GET of
>http://www.w3.org/People/Connolly/ returns a 2xx status, then
>http://www.w3.org/People/Connolly/ is an "information resource".
>
>The WebArch says that the meaning of the fragment identifier ("#me") is
>determined by the media type that is returned.  In the case of HTML, it
>identifies a location with the HTML document.  Therefore, according to
>the WebArch plus the httpRange-14 decision,

/+ if the HTTP GET returns 200 OK with Content-Type: text/html then +/

>http://www.w3.org/People/Connolly/#me identifies a location within an
>HTML document. 

(This might be an distinct "information resource" too, with a relationship
to the containing information resource, or it might be just a location
within an information resource.  Which of these it is may matter to
some but it's not the crux of this message.)

>If Dan is also using http://www.w3.org/People/Connolly/#me to identify a
>foaf:Person (for example by also serving RDF from
>http://www.w3.org/People/Connolly/ )

/+ via 200 OK with Content-Type: application/rdf+xml +/

>, then the same URI is being used
>both to identify a foaf:Person and an "information resource".  Is this
>okay?  Pat Hayes does not see this as a problem, as he has eloquently
>explained[6].  However, the WebArch says that a URI should only identify
>one resource, so this behavior seems inconsistent with the WebArch.  
...

>Is it reasonable to think that the use of
>http://www.w3.org/People/Connolly/#me as a location within a document
>would be "sufficiently consistent" with its use as a foaf:Person?

(This is a rhetorical question, right?  We don't expect the TAG to
answer it for us, rather the [Semantic] Web community decides.)

This dual use of identifiers becomes yet more explicit when a
technology such as GRDDL [9] is employed.  It seems likely
that authors of XHTML documents that offer GRDDL transforms
might be tempted to use XML IDs as both HTML fragment ids
and as the identifiers of instances of other things.

[9] http://www.w3.org/TeamSubmission/2005/SUBM-grddl-20050516/

>On the other hand, if it *is* reasonable to use
>http://www.w3.org/People/Connolly/#me as both a location within a
>document and as a foaf:Person, then is it also reasonable to use
>http://example.org/foo as both an "information resource" and a
>foaf:Person?  If not, why is a URI with a fragment identifier permitted
>to simultaneously identify such different things, while a URI without a
>fragment identifier is not.  

(I could imagine an argument based on the notion of fragment
identifiers as "views" --- with the interpretation of a "view" being
left to each application but informed by the Content Type.  Thus,
the '#' serves as a kind of escape mechanism allowing the
client some freedom to interpret the 200 OK response in some
locally-determined contextual manner.)

>Furthermore, if http://example.org/foo return a 2xx response, does this
>represent an assertion such as (N3):
>
>        <http://example.org/foo> a tag:InformationResource .
>
>If so, what can be concluded if the response code is other than 2xx, 4xx
>or 303?  In general, what algorithm should be used to determine the
>meaning of a newly discovered URI?  (See David Booth's attempt at

See /+[7]+/David Booth's attempt at...

>writing down such an algorithm based on his reading of the WebArch and
>httpRange-14 decision.)

-Ralph
Received on Friday, 17 February 2006 15:05:25 UTC

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