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

Datatypes in RDF (was: RDFCore Update)

From: Eric van der Vlist <vdv@dyomedea.com>
Date: Fri, 19 Oct 2001 10:18:31 +0200
Message-ID: <3BCFE1D7.2070507@dyomedea.com>
Cc: www-rdf-interest@w3.org
Hi,

Patrick.Stickler@nokia.com wrote:


> 
> One would presume that all of the following three examples
> define precisely the same knowledge regarding data types:
> 
> --
> 
> <rdf:Description rdf:about="urn:foo:bar">
>   <abc:someProperty>
>     <rdf:Description>
>       <rdf:type rdf:resource="x:dataType"/>
>       <rdf:value>dataValue</rdf:value>
>     </rdf:Description>
>   </abc:someProperty>
> </rdf:Description>
> 


<rant>
Although many vocabularies are doing so I am usually very reluctant to 
use qualified names in attributes or element values.

I think that markup languages should be considered as layered 
architecture (like communication protocols) and that the association 
between a namespace URI and a namespace prefix belongs to "layer2: 
namespaces" and should be used only at this level.

Not doing so exposes to tricky issues such as the restrictions in 
cannonical XML [1] which has not been able to include prefix rewriting 
in its scope and XPointer which has discovered that namespaces prefix 
were context dependent.

[1] http://www.w3.org/TR/2001/REC-xml-c14n-20010315
[2] http://xmlhack.com/read.php?item=982
</rant>

This being said, I think that you may want to acknowledge that W3C XML 
Schema types can already be defined in instance documents, and even in 
RDF instance documents and you may want to define some compatibility with:

<?xml version="1.0" encoding="iso-8859-1"?>

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
	xmlns="http://example.org/xsi#"
	xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

  <foo xsi:type="foo-type" rdf:about="http://example.org/subject">
  	<bar>123</bar>
  </foo>

</rdf:RDF>

Unfortunately, it's working with "elements only complex contents" but 
not with simple types and <bar xsi:type="xs:integer">123</bar> 
wouldn't be valid RDF!

Additionaly, I'd like to mention a discussion [3] about annotating XML 
documents with PSVI information which may also be relevant to this 
discussion.

[3] http://lists.xml.org/archives/xml-dev/200110/threads.html#00556

Hope this helps.

Eric
-- 
Rendez-vous  Paris pour le Forum XML.
                    http://www.technoforum.fr/Pages/forumXML01/index.html
------------------------------------------------------------------------
Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
http://xsltunit.org      http://4xt.org           http://examplotron.org
------------------------------------------------------------------------
Received on Friday, 19 October 2001 04:18:08 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:52 GMT