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

RE: Summary of the QName to URI Mapping Problem

From: <Patrick.Stickler@nokia.com>
Date: Fri, 17 Aug 2001 15:33:23 +0300
Message-ID: <2BF0AD29BC31FE46B78877321144043114B528@trebe003.NOE.Nokia.com>
To: connolly@w3.org
Cc: drew.mcdermott@yale.edu, www-rdf-logic@w3.org, www-rdf-interest@w3.org
> > > [This will be my last message in this thread unless/until
> > > I see some new information. We're convering well-trodden
> > > ground here. cf
> > > http://www.w3.org/2000/03/rdf-tracking/#rdfms-uri-substructure ]
> > 
> > Well trodden but hidden ground? Sorry, I don't see how your 
> reference
> > does anything but reiterate that there is an issue here.
> 
> That's all the pointer was meant to do.
> 
> But I did get some new information out of your most recent
> message: you're trying to match qnames in RDF without
> expanding them to URIs; for example, using XSLT.

Exactly. Because there is *no* possible generic function for combining
a namespace and name into a URI which will not either potentially result
in ambiguity, or result in an invalid URI scheme syntax, or have an
invalid fragment syntax, for any arbitrary namespace URI.

c.f. the arguments in
http://lists.w3.org/Archives/Public/www-rdf-interest/2001Jun/0151.html

The only option is to say ('namespace')('name') <-> URI   

Note that the mapping is bidirectional... so we can re-serialize a URI for
a specific namespace with a name that some other application that
knows about that namespace will recognize.

> I have to admit I do that myself from time to time...

I just think it's something that should be provided for in an
efficient and standardized fashion by every RDF parser. Because,
even though you might have a mapping filter for your SW agent
or application, that doesn't mean all SW agents or applications
will, and therfore we fail to have consistency in resource naming
on a global scale because your local mapping might be other than what 
is achieved by direct concatenation by some remote system.
 

> > Uhhh, but if the actual QNames needed, according to the actual
> > ontology are (mid:xyz@foo)(ble) and (mid:xyz@foo)(ble1) and
> > you have applications, style sheets, etc. etc. looking for the
> > real QNames, just what do you expect them to do with the above
> > guesses.
> 
> I don't expect "real ontologies" to deal with Qnames... just URIs.

I meant, XML (non-RDF) applications which deal with "real" ontologies
with specific namespaces and names, and the ability of such applications
to exchange information with any arbitrary RDF system, not just one
which has the needed precise mappings hard-coded...

> But XSLT is kinda handy... the actual mapping convention I tend
> to use in practice is:
> 
> I. If you're designing and RDF vocabulary and you
> want to make it easy to use XSLT with it,
> choose a namespace name that ends in a non-XML-name character
> (e.g. # or / or ?)

But you may not have the luxury of choosing your namespace. Whatever
method is used must not discriminate against any URI scheme in
any way.

> II. to split a URI ...
> 
> In fact... this is what TimBL implemented in the semantic web toolkit
> we're hacking on:

Sure, that works for special namespace URIs, but not for any arbitrary
URI, and it IMO should work for any arbitrary URI if we are talking about
a global, critical mass of interoperable knowledge for the SW. No?

Cheers,

Patrick

--
Patrick Stickler                      Phone:  +358 3 356 0209
Senior Research Scientist             Mobile: +358 50 483 9453
Software Technology Laboratory        Fax:    +358 7180 35409
Nokia Research Center                 Video:  +358 3 356 0209 / 4227
Visiokatu 1, 33720 Tampere, Finland   Email:  patrick.stickler@nokia.com
 
Received on Friday, 17 August 2001 08:33:50 GMT

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