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Re: XQuery and RDF datatypes was: RDF specifications

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 06 Dec 2001 08:07:25 -0500
To: jborden@mediaone.net
Cc: www-rdf-interest@w3.org
Message-Id: <20011206080725V.pfps@research.bell-labs.com>
From: "Jonathan Borden" <jborden@mediaone.net>
Subject: Re: XQuery and RDF datatypes was: RDF specifications
Date: Wed, 5 Dec 2001 19:22:05 -0500

> Peter F. Patel-Schneider wrote:
> For simple types like "integer" and "float", I agree (XML 1.0 itself defines
> defines a set of attribute types derived from SGML types), and for these XML
> Schema does specify URI references. On the other hand DAML+OIL suggests that
> XML Schema can be used for general datatypes. This poses a problem as I and
> others have discussed before:
> http://www.xmlhack.com/read.php?item=1137
> For example (from a document you are well familiar with
> http://www.daml.org/2001/03/daml+oil-walkthru.html#individuals) where it is
> suggested that an XML Schema document can be referenced:


> What you _wish_ to do is to use the value of the _name_ attribute as a
> fragment identifier, correct? Firstly, the _actual_ XML Namespace for XML
> Schema is http://www.w3.org/2001/XMLSchema (i.e. without the trailing '#',
> which turns out to be important because if the "xsd" prefix is then used in
> an RDF document ala <xsd:integer>5</xsd:integer> it will parse (via RDF)
> rules to the URI http://www.w3.org/2001/XMLSchemainteger --- which is not
> what you want)

Actually, using constructed XML Schema datatypes as classes (for ranges) is
an optional aspect of my proposal, and not even really in my message in
this thread.  The basic idea is to use the type information from XML Schema
validation to provide the lexical-to-value mapping information needed to
make literals unambiguous.

The DAML+OIL method goes further, and may have its own problems, which
would be separate from any problems with using post-schema validation

> Secondly, the "name" attribute in an XML Schema document is NOT of type ID,
> i.e. is not used to create fragment identifiers. The problem is that "name"s
> are not required to be unique in XML Schema, i.e. it is entirely possible to
> have all of the above in a single schema:
> <xsd:element name="foo"> ...
> <xsd:attribute name="foo"> ...
> <xsd:simpleType name="foo"> ...
> <xsd:complexType name="foo"> ...
> !!!
> The XML Schema Formal Description discusses this specific issue and proposes
> a _new_ URI syntax which does properly identify XML Schema items _but not by
> name="foo"_

It may be necessary to use a different naming method to identify
constructed XML Schema datatypes.  It may also be the case that some XML
Schema documents are not suitable for use in RDF or DAML+OIL.  It would be
up to whoever defines the way that RDF and XML Schema documents interact to
iron out these problems.  (And we did probably get some things wrong in the
DAML+OIL way of providing this interaction.)


> Jonathan

Received on Thursday, 6 December 2001 08:08:38 UTC

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