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Re: Are URI-References bound to resources?

From: Dan Connolly <connolly@w3.org>
Date: Fri, 11 May 2001 14:18:38 -0500
Message-ID: <3AFC3B0E.3444B20F@w3.org>
To: Aaron Swartz <aswartz@upclink.com>
CC: uri@w3.org
Aaron Swartz wrote:
> 
> In RDF, I've seen people binding URIs like:
> 
> http://example.org/q#foo
>   and
> http://example.org/q#bar
> 
> to different resources. The URI spec clearly says:
> 
> <q cite="http://www.ietf.org/rfc/rfc2396.txt">
>    A Uniform Resource Identifier (URI) is a compact string of characters
>    for identifying an abstract or physical resource.
> </q>
> 
> but later when it defines URI references, it says:
> 
> <q>
>    The term "URI-reference" is used here to denote the common usage of a
>    resource identifier.  A URI reference may be absolute or relative,
>    and may have additional information attached in the form of a
>    fragment identifier.  However, "the URI" that results from such a
>    reference includes only the absolute URI after the fragment
>    identifier (if any) is removed and after any relative URI is resolved
>    to its absolute form.
> </q>
> 
> This seems to imply that URI references (that is, URIs with fragment
> identifiers) are not bound to a resource themselves.

Careful... it does not imply that URI references are
bound to resources; but nor does it imply that they are *not*
bound to resources. RFC2396 is silent on what
a URI reference is bound to.

> Instead, the only
> resource involved is that of the absolute URI itself.
> 
> Is this interpretation correct?

I don't think so; I think you're reading more into RFC2396
than is there. (you're certainly not the first, and
I don't expect you'll be the last.)

> If so, it would have serious consequences
> for many RDF specifications.

RDF isn't the only spec that extends the domain
of the URI->resource mapping; XLink does too--
er... it did in earlier drafts... I pointed
that out in a review comment... during last call,
I think; they seem to have changed their mind since then...

[[[
The notion of resources is universal to the World Wide Web. [Definition:
As
discussed in [IETF RFC 2396], a resource is any addressable unit of
information or service.] Examples include files, images, documents,
programs, and query results. The means used for addressing a resource is
a URI (Uniform Resource Identifier) reference (described more in 5.4
Locator Attribute (href)). It is possible to address a portion of a
resource.
]]]

--        XML Linking Language (XLink) Version 1.0
http://www.w3.org/TR/2000/PR-xlink-20001220/#N789
Wed, 20 Dec 2000 19:11:04 GMT

Keep in mind that RDF 1.0 was finished Feb 1999,
just a few months after RFC2396 in Aug 1998. It would
seem perfectly reasonable to do an editorial revision
of RDF to make a new term for what RDF 1.0 calls 'resource',
and use 'resource' to mean just what RFC2396 defines
it to mean.

TimBL went that way in some code he wrote recently;
he uses 'Thing' for the class of things that includes
resources *and* things denoted by absolute-uris-with-fragments:

########################################  Storage URI Handling
#
#  In general an RDf resource - here a Thing, has a uriRef rather
# than just a URI.  It has subclasses of Resource and Fragment.
# (libwww equivalent HTParentAnchor and HTChildAnchor IIRC)
#
-- http://www.w3.org/2000/10/swap/cwm.py


Hmm... my index of terms could use updating...
  http://www.w3.org/Architecture/Terms#resource
  http://www.w3.org/Architecture/Terms#anchor-address

I should make that a Semantic Web thingy, ala the
index of URI schemes.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 11 May 2001 15:19:00 GMT

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