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a rathole issue? - non denoting terms/URIs

From: Dan Brickley <danbri@w3.org>
Date: Mon, 18 Mar 2002 15:23:25 -0500 (EST)
To: Pat Hayes <phayes@ai.uwf.edu>
cc: <www-archive@w3.org>
Message-ID: <Pine.LNX.4.30.0203181512131.23139-100000@tux.w3.org>


Pat,

I've been thinking about a rathole topic that I tried to avoid in RDFCore
last time it cropped up. A sanity check or logician's perspective would be
welcome.

Issue is URI-refs that while syntatically well formed per RFC2396, don't
denote anything. Much of the RDF formalisation assumes that terms denote,
but we need to deploy RDF in a Web where things aren't so clean. Example:

xyz://foo.bar/
http://example.com/
urn:bogus-ns:etc

These look and smell like URIrefs, and we can probably call them such, but
(on some readings of the web-arch tealeaves) don't name anything.

Two thoughts:

(i) our lives might be easier if we could get web architectural blessing
for the simplifying assumption that all Web names (URI-refs) denote
something (perhaps defaulting to a /dev/null object). But if we can't
asume this...

(ii) a statement composed of a term that doesn't refer (assume some
bogus URI scheme which will be bogus in all interpretations) is never
going to be true. a graph containing such a statement isn't a healthy
looking truth  candidate either. I fear this means that bad/wrong/typo'd data, even if
reified, will infect the truth-prospects of any RDF document that includes
a reification of it (since reification doesn't currently stringify
names/uris).

eg
	<rdf:Statement>
	 <rdf:subject rdf:resource="xyz://foo.bar/"/>
	</rdf:Statement>

if xyz://foo.bar/ is a 'bad URI', one can't even reify statements that use
it without getting into trouble. Contrast with, for example,


	<rdf:Statement>
	 <rdf2:subjectTerm rdf2:stringifiedURI="xyz://foo.bar/"/>
	</rdf:Statement>

...which has some hope of being true, even if xyz://foo.bar/ is non-denoting.


A rushed scribble cos a saw you were online. Am I making any sense?

Copying www-archive for future reference,

Dan
Received on Monday, 18 March 2002 15:23:26 GMT

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