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RE: What to do about namespace derived URI refs... (long)

From: <Patrick.Stickler@nokia.com>
Date: Wed, 6 Jun 2001 18:44:10 +0300
Message-ID: <6D1A8E7871B9D211B3B00008C7490AA50795872A@treis03nok>
To: jborden@mediaone.net, Patrick.Stickler@nokia.com, www-rdf-interest@w3.org
Cc: Ora.Lassila@nokia.com

Exactly! If I e.g. want to use XML Schema to provide strict
data typing for my serialized RDF instances (e.g. strict
date formats, enumerations of token value sets such as
ISO language names, etc.) I need to be sure that both XML
Schema and RDF Schema are using the same URIs to talk about
the same things.

If I try to use a class in an XML Schema as a superclass of
an RDF class, per the DAML examples, then I run into all
kinds of nastiness.

Likewise, if I wish to define enumerations of token values for
a property in XML Schema and then assign rankings (numeric
values) for those in RDF Schema, the URI ref I have to use
is tied to the XML Schema MIME content type and is not generic
and portable, as it should be.

   XML Enumeration for 'status'         RDF assigned rank
   ---------------------------          -----------------
           draft                                1
        draft_approved                          2
         approved                               3
          retired                               4

(the rank is needed if I want to have queries such as
 'status <= approved', etc.)

Tricky, yes. Though I'd use a stronger term ;-)

Thanks for the pointer to your algebra materials. I'll have a look.

Cheers,

Patrick

> -----Original Message-----
> From: ext Jonathan Borden [mailto:jborden@mediaone.net]
> Sent: 06 June, 2001 18:17
> To: Patrick.Stickler@nokia.com; www-rdf-interest@w3.org
> Cc: Ora.Lassila@nokia.com
> Subject: Re: What to do about namespace derived URI refs... (long)
> 
> 
> Ok I see. What is tricky about _that_ problem is that the fragment
> identifier syntax is defined by the media type of the MIME 
> message. I have
> started to consider these issues: 
> http://www.rddl.org/SchemaAlgebra . There
> are some thorny issues here. Consider particularly the fact 
> that XML Schema
> uses QNames not URI references to generally identify types, 
> and that a QName
> may identify each an element, attribute, complexType etc.
> 
> -Jonathan
> 
> 
> 
> >
> > No, this is still missing the point. Even if I am able
> > to use RDDL to retrieve a DTD, an XML Schema, an RDF Schema,
> > etc. etc. associated with a namespace, that *still* does
> > not address the problem that the abstract information
> > resources (e.g. properties, etc.) defined in any of those
> > schemas may have varying URI references!
> >
> > There should be, e.g. for the DC 'Title' property, one consistent
> > URI reference that can be used by RDF Schemas to reference it, and
> > that URI reference should be the same regardless as to whether
> > my system is using a DTD, an XML Schema, or any other schema
> > to define well formedness or validity constraints on the 
> serialization
> > of data streams for interchange into/out of that system.
> >
> > I think that RDDL solves a very important problem, but that's not
> > the problem I'm talking about here.
> >
> > Patrick
> >
> > > -----Original Message-----
> > > From: ext Jonathan Borden [mailto:jborden@mediaone.net]
> > > Sent: 06 June, 2001 17:25
> > > To: Patrick.Stickler@nokia.com; sean@mysterylights.com;
> > > www-rdf-interest@w3.org
> > > Cc: Ora.Lassila@nokia.com
> > > Subject: Re: What to do about namespace derived URI refs... (long)
> > >
> > >
> > >
> > > >
> > > > The key point here is that (a) we use URNs rather than URLs
> > > > to identify namespaces and abstract resources, and (b) we
> > > > define the necessary mappings between a standardized URN
> > > > scheme and the various schema and serialization schemes
> > > > that might reify or reference those abstract resources
> > > > within a given system (i.e. XML Schema, RDF, etc.).
> > > >
> > >
> > > The XML-DEV group has been discussing this issue at length. RDDL
> > > http://www.rddl.org is suggested as a format to describe
> > > namespace related
> > > resources such as schemata, CSS etc. A RDDL document may be
> > > resolved by a
> > > URL, or via a URN using something like the DDDS mechanism:
> > > 
http://www.ietf.org/internet-drafts/draft-ietf-urn-uri-res-ddds-03.txt
> >
> > -Jonathan
> >
>
Received on Wednesday, 6 June 2001 11:44:46 GMT

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