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Re: [namespaceDocument-8] Proposal: "Namespace Document" = RDF

From: Jonathan Borden <jonathan@openhealth.org>
Date: Fri, 8 Mar 2002 11:33:51 -0500
Message-ID: <057001c1c6bf$095149e0$0a2e249b@nemc.org>
To: "Patrick Stickler" <patrick.stickler@nokia.com>, "ext Elliotte Rusty Harold" <elharo@metalab.unc.edu>, "WWW TAG" <www-tag@w3.org>
Patrick Stickler wrote:
>
> See above. RDDL as presently defined does not appear to
> be able to describe arbitrary resources denoted by URIs,
> but only to describe a "namespace", which is odd, since
> there's not much one can actually say about punctuation...
>

a) This discussion is _about_ "Namespace Documents". Any inability to
describe arbitrary resources is not within the scope of this discussion.

b) to quote the RDDL spec:
[[
This document describes the Resource Directory Description Language (RDDL).
A RDDL document, called a Resource Directory, provides a package of
information about some target, including:
]]

Nowhere does it say that RDDL is limited to the description of namespaces (I
can assure you of that). Nonetheless RDDL was not designed as a replacement
for RDF.

c) You have asked about the ability to describe an "arbitrary" resource in a
RDDL document.
The XLink spec is not explicit about the source URI reference for a simple
XLink, however extrapolating from RFC 2396 and XML Base, a xml:base
attribute attached to a rddl:resource element may be used to assist in the
assignment of a source URI reference for the arc described by the
rddl:resource XLink. From RFC 2396 4.2:

[[
   However, if the URI reference occurs in a context that is always
   intended to result in a new request, as in the case of HTML's FORM
   element, then an empty URI reference represents the base URI ...
]]

This is not crystal clear, at least to me, but I suggest that:

<rddl:resource xml:base="http://example.org/source"
            xl:href="http://example.org/dest"
            xl:arcrole="http://example.org/predicate"
/>

may be interpreted to represent the triple: [<source> --predicate--> <dest>]

<http://example.org/source> <http://example.org/predicate>
<http://example.org/dest> .

Similarly the use of the ID attribute defines the source with respect to a
"term" in the namespace:

<rddl:resource xml:base="http://example.org/source" id="foo"
            xl:arcrole="http://example.org/predicate"
            xl:href="http://example.org/dest"
/>
<http://example.org/source#foo> <http://example.org/predicate>
<http://example.org/dest> .

So you see that by incorporating xml:base (which RDDL does), the RDDL syntax
is very close to the RDF N-Triples syntax. This was not an accident.

Indeed one can argue, I think successfully, that the XLink syntax is closer
to RDF N-Triples than the RDF XML syntax. It also has the property of being
able to serialize an arbitrary RDF graph.

From an architectural point of view, it would be good to more
officially/explicitly specify the relationship between XLink and RDF (the
current interpretation is from Ron Daniel's W3C Note)

Jonathan
Received on Friday, 8 March 2002 11:36:34 GMT

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