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Re: semantics and RDF(S)

From: Dan Brickley <danbri@w3.org>
Date: Fri, 12 Jan 2001 09:34:17 -0500 (EST)
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
cc: <www-rdf-logic@w3.org>
Message-ID: <Pine.LNX.4.30.0101120905150.4428-100000@tux.w3.org>

Peter,

On Fri, 12 Jan 2001, Peter F. Patel-Schneider wrote:

> In the process of working on the design of DAML+OIL, I have had extensive
> dealings with RDF and RDF Schema.  In this message I present the biggest
> problem that I see with RDF and RDF Schema.

> [...] How can I build a notion of cardinality
> when there is no notion of equality for much of RDF and RDF Schema?

In the process of working on and with RDF, similar issues have bothered
me. Most specifically, concerns surrounding our notion of identity,
resource naming and the connection between URIs and the things they
supposedly name.

RDF is a technology of and for the Web; it needs to play well with other
W3C and IETF specifications (HTTP, XML, URI/URL...); as such RDF adopted
rather than invented notions such as 'resource','URI','URI reference'
etc., pointing off to other specs for the (sometimes hotly debated)
detail.

If RDF is guilty of inclarity, that guilt comes at least partly through
association with the equally muddy Web architectural principles embodied
in those other specs. If RDF (and/or DAML+OIL, RuleML or whatever) is to
prove effective for reasoning about content on the Web, it's not good
enough simply to have a clean notion of resource naming within the RDF
or DAML spec. Those notions need to be applied and understood across the
board -- in HTTP's notion of resource; in XML  namespace naming, in XPointer,
XLink, URI References versus URIs  and on and on. That kind of cleanup is
a huge task, and one I believe the RDF Model and Syntax WG were wise to
avoid for RDF '1.0'.

While identity/naming/equality wasn't the only issue you raised, it is
IMHO at the centre of most of the confusion we've seen, and a precondition
for clarity on the other issues you mention. In my view you're
right to be frustrated, but have the wrong target. The thing to clean up
first is the general notion of URI naming on the Web; if we get that
right, a crisper view of RDF should fall out more or less for free.

In a nutshell: formalise URIs and you fix a bunch of stuff at once;
formalise RDF and you'll still have to map it to a load of specs that have
differing notions of URI, resource, URI reference etc.

Dan


ps. for some pointers back to the various docs describing notions of Web
'resource' see the links I just posted to the main RDF list;
http://lists.w3.org/Archives/Public/www-rdf-interest/2001Jan/0104.html

for an example of confusion and debate on these issues in a non-RDF
context, see the XML-URI archives for May/June last summer.

http://lists.w3.org/Archives/Public/xml-uri/2000May/
Received on Friday, 12 January 2001 09:34:23 GMT

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