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

RE: Summary of the QName to URI Mapping Problem

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 17 Aug 2001 14:57:49 -0700
Message-Id: <v04210105b7a340774255@[]>
To: Patrick.Stickler@nokia.com
Cc: www-rdf-logic@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
>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.

But havnt you just pointed out that that is impossible? So what do 
you propose we do?

> > 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?

Maybe I'm missing something here, but you seem to be assuming that 
there is masses of information out there for the SW to use, all 
written in free-form XML (not RDF, or DAML+OIL, or whatever). Never 
mind the Qname-to-URI mappings; I find this wildly implausible on 
other grounds. For a start, there isn't any semantics for XML, so 
what possible inferences could any software engines draw from 
free-form XML (even if they do get their names lined up properly) ? 
Ontologies, "real" or otherwise, require an ontology language. God 
knows, RDF isn't much of an ontology language, but it does have at 
least a *glimmer* of propositional content; but XML is just a 
notation for marking up text with labels and for describing labelled 
directed graphs.

Pat Hayes

(650)859 6569 w
(650)494 3973 h (until September)
Received on Friday, 17 August 2001 17:57:04 UTC

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