W3C home > Mailing lists > Public > www-rdf-interest@w3.org > November 2001

Re: RDF statements' equivalence.

From: Dan Pokorny <dan@gingerall.cz>
Date: Fri, 09 Nov 2001 14:14:33 +0100
Message-ID: <3BEBD6B9.5030603@gingerall.cz>
To: www-rdf-interest@w3.org
Thomas B. Passin wrote:

> [NAMESPACES] makes a clear distinction between a URI refernce as used 
> for a
> namespace and a URI as used (functionally) as a URI reference:
> "[Definition:] URI references which identify namespaces are considered
> identical when they are exactly the same character-for-character. Note 
> that
> URI references which are not identical in this sense may in fact be
> functionally equivalent. Examples include URI references which differ 
> only
> in case, or which are in external entities which have different effective
> base URIs. "
> According to this, there is no contradiction, and the two triples are not
> equivalent.
Resources are identified by a /resource identifier/. A resource 
identifier is URI
plus an optional anchor id. We have two different resources here (the 
properties, as they
come from different namespaces according to [NAMESPACES]) that are 
identified by one
URI plus the anchor id. I think that "is identified" means that there is 
(at most) one identified
thing for one identifying thing. Am I wrong?

> However, there is a different problem lurking here.  According to 
> [URI], a
> "URI Reference"  by definition means what you have after the fragment
> identifier has been removed.  Therefore, by definition,
> http://www.foo.com/ns#p1 cannot be a URI reference!  In fact, the RDF M&S
> refers to URI plus optional anchor id, not to URI reference.
> So [NAMESPACES] uses URI references, and RDF uses URI+fragment 
> identifier.
> Hmm, what to do?
URI reference can contain a fragment identifier.
 From [URI]:

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.

URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]

Dan Pokorny
Received on Friday, 9 November 2001 08:14:56 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:07:38 UTC