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RE: RDF Schema and XML Schema Part 2: Datatypes

Eric van der Vlist wrote:

> The latest version of DAML+OIL [1] is proposing some answers to these
> questions.
> Some assumptions made here may be considered controversial but the whole
> construct seems coherent.

The only problem is that this version of DAML+OIL uses the wrong namespace
for XML Schema, the RDFism: http://www.w3.org/2000/10/XMLSchema# -- while
this 'works' for RDF the trailing '#' means that it is a completely
different namespace ... that is, namespace names cannot be sort of equal, or
almost equal, they either are or are not equal.

The practical effect of this is that XML Schema software will not recognize
the document: http://www.daml.org/2001/03/daml+oil-ex-dt.xsd because the
root schema element is not in the XML Schema namespace.

Another problem relates to the assignment of URIs for XSD types which are
specified as QNames. This issue has been gone over in detail and while I
have discussed some small changes that IMHO ought be made to the RDF XML
syntax, the RDF and XML Schema typing mechanisms are unfortunately
incompatible as they currently stand.

It is not currently possible in general to identify an XML Schema datatype
with a URI -- and even if it were such URIs would not be compatible with the
RDF typedNode XML syntax.

Moreover the MSL introduces an entirely new fragment identifier syntax for
XML Schema types (e.g. foo#type::element::bar) which is also totally
incompatible with RDF.

So while I would very much like to see an integrated RDF and XML Schema
typing mechanism, and while there is a substantial W3C representation on the
DAML team, this integration doesn't work.


> [1] http://xmlhack.com/read.php?item=1137
> Lee Iverson wrote:
> >
> > A simple question as I'm getting up to speed with some of this.  How
> > does one integrate the data typing mechanisms in RDF Schema and XML
> > Schema Part 2?  In particular, I'm interested in defining an
> > RDF Schema that constrains the types of certain values using
> > <simpleType> references from the datatypes specification.  Does anyone
> > have some examples or papers they can point me to?
> >
> >