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

RE: Linking RDF

From: Lee Jonas <lee.jonas@cakehouse.co.uk>
Date: Fri, 20 Apr 2001 16:42:23 +0100
Message-ID: <51ED29F31E20D411AAFD00105A4CD7A770FD@zingiber.cakehouse.co.uk>
To: "'Murray Altheim'" <altheim@eng.sun.com>, "Sean B. Palmer" <sean@mysterylights.com>
Cc: "'www-rdf-interest@w3.org'" <www-rdf-interest@w3.org>
Murray Altheim [mailto:altheim@eng.sun.com] wrote:

>"Sean B. Palmer" wrote:
[snip]
>> 
>> In that case, I think that a useful thing that
>> the HTML specification could have defined is that any link types get
>> concatenated onto the profile attribute content, a bit like a QName,
>> so that:-
>> 
>> <head profile="http://example.org/#">
>> <link rel="meta" [...]
>
>Except that 'profile' is really not going anywhere, from what I have
>heard over the last few years in the HTML WG. Underdefined, overloaded,
>who knows. The remnant of a dying world, perhaps. Gad. Get me some 
>coffee.
> 
>> is defined by http://example.org/#meta
>
>BTW, I musta been out of the country for this one. Where in the world 
>did the idea of appending "#" to the *end* of a URL come from? Seems 
>very weird or just wrong. I don't know of a file system that likes files
>named "#", and I don't want to *always* rely on a web server to patch
>me through to index.html or whatever. Anyone? What does this mean?
> 
>
>Murray
>

This is a legacy of the current RDF 1.0 spec.  It seems the RDF spec went
out on a tangeant from other XML based specs and treats namespaces not as a
namespaceURI+localpart pair, but as the concatenation of the two to produce
a URI-reference.  

Hence <rdfs:Class xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" ... />
means that the RDF resource, 'rdfs:Class', *may* be defined by the
URI-reference 'http://www.w3.org/2000/01/rdf-schema#Class' (if the URI
actually resolves to a resource representation at all).

There are three problems this 'interpretation' of namespaces gives us: open
grammar, which is harder to validate simply (and nigh on impossible to do
properly with DTDs); weird, unwieldy namespaces with different semantics to
other XML namespaces; resolution of RDF schemas clashes with resolution of
XML schemas.

My views:
Without seeming too antagonistic, IMHO this is one of the poorer decisions
made by the creators of RDF 1.0.  It also demonstrates a lack of necessary
structure in place at the W3C to promote coordination between different XML
initiatives (esp. ensuring consistency between RDF, XHTML, XML Namespaces,
XML Schema).  Only now, after RDF has become a W3C Recommendation, are we
trying to figure out how to get them to play together nicely :-(

Discussions on these issues seem to have died down, yet the issues have not
been resolved and the new RDFCore working group are not even going to
address them.  It seems that these aspects will not get reviewed for some
time to come.  A pity.

One thing is for sure: It is one of a few problematic areas that make
discussions about integrating RDF as it currently stands with other XML
grammars so perplexing right now.

regards

Lee


>...........................................................................
>Murray Altheim, SGML/XML Grease Monkey     <mailto:altheim&#64;eng.sun.com>
>XML Technology Center
>Sun Microsystems, 1601 Willow Rd., MS UMPK17-102, Menlo Park, CA 94025
>
>      the wood louse sits on a splinter and sings to the rising sap
>      ain't it awful how winter lingers in springtimes lap -- archy
>
Received on Friday, 20 April 2001 11:42:18 GMT

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