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Murali Mani wrote:
>I had a question:
>
>What role does XML Schema play in semantic web?
>
>
>In specific, do you think search engines will use XML Schemas at all?? Or
>are there other applications of semantic web that will use XML schemas??
>
>
The specific area where RDF and OWL use XML Schemas is for datatypes and
owl:DatatypeProperty's -- currently only for simple datatypes, but
hopefully in the future for complex i.e. XML datatypes.
The current problem in integrating XML Schema with RDF/OWL _XML_
datatypes is that RDF is entirely based on naming things with URIrefs
(and hence OWL), whereas XML Schema names things (i.e. schema
components) with QNames. A reasonable integration requires a coherent
QName -> URI mapping.
If such a mapping were to exist, there is no reason why RDF literals
might not be typed by their XML Schema type name (the URIref version
:-), and hence no reason why a Semantic Web query might not be
constained by XML Schema types e.g.
<owl:DatatypeProperty rdf:ID="foo">
<rdfs:range
rdf:resource="http://example.org/XMLSchema/someXMLtype"; />
</owl:DatatypeProperty>
where http://example.org/XMLSchema/someXMLtype identifies a complex type
in an XML Schema. One might similarly use XPointers to create datatypes
that match patterns.
In any case there have been discussions of this on the WebOnt WG lists
e.g. around
http://lists.w3.org/Archives/Public/www-webont-wg/2002Nov/0037.html .
I've written up some of the issues at:
http://www.openhealth.org/WOWG/IssueStructuredDatatypes.html
as well as the discussion on www-rdf-comments: (around)
http://lists.w3.org/Archives/Public/www-rdf-comments/2002OctDec/0073.html
So, I'd say the answer is that there is no great technical impediment to
better integrating XML Schema (and RELAXNG for that matter) with the
Semantic Web via RDF datatypes, but unless there is an interest voiced
(other than mine) in the proper forums, that the (perhaps) relatively
small amount of work to accomplish this might not get done.
Jonathan
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