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RE: In Search of XML Interoperability: XLink + XML Schema = Interoperability?

From: Jean Marc VANEL <jean-marc_vanel@effix.fr>
Date: Thu, 17 Feb 2000 19:32:53 +0100
To: David Wang <dwang@mitre.org>, xml-dev@xml.org, www-rdf-interest@w3.org, jmvanel@free.fr
Message-ID: <C1256888.0065E045.00@smtpnotes.effix.fr>


In this search for Interoperability, I want to advocate for another way of linking things than Xlink: it's RDF.

What is RDF's advantage compared to Xlink ?

Instead of inventing new xlink attributes, e.g. this had been suggested:

isA | hasA | equiv | isLike | partOf

RDF allows to link two resources WITH ANY DOMAIN-DEFINED SEMANTICS.
I'll give examples, and list afterwards the architectural implications.

1rst example:
Express that yourElement in your XML Schema has the equivClass attribute with a value being myElement in my XML Schema (i.e. the two elements have same type).

<rdf:RDF xmlns:RDF="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:xs ="http://www.w3.org/TR/1999/WD-xmlschema-1-19991217" >
  <rdf:Description about="http://yourCom.com/yourXMLSchema.xs#yourElement">
    <xs:equivClass>http://myCom.com/myXMLSchema.xs#myElement</xs:equivClass>
  </rdf:Description>
</rdf:RDF>

2nd example:
One wants to mark a paragraph in a document as obsolete.

<rdf:RDF xmlns:RDF="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:doc="http://myCom.com/documents.rdf">
  <rdf:Description about="http://myCom.com/department/reports/2000-01.html#someParagraph">
    <doc:status>obsolete</doc:status>
  </rdf:Description>
</rdf:RDF>

3rd example:
In mechanical construction, one wants to add information to a component defined in a geometrical CAD document about material, or supplier, etc.

4th example:
In a Virtual Reality document, I could change the position or orientation of an object, and thus realize a movement or a sudden change in the scene.

Architectural implications
- the RDF document adding or modifying the subject resource can be either local and private, or published on a LAN or the Web;
- the subject resource that is being described can be ANYWHERE.
- the element or attribute in the "about" part of the RDF statement must be accessible as a URI; generally it will be marked with an attribute of XML ID type, but if Xpointer is supported, an XPath
syntax is possible;
- the domain-specific processors, (in the examples Schema processor, word processor, CAD processor) must be RDF-aware, that is able to read a set of  rdf:Description  , and apply the given properties
to the given resources, if it knows about theses properties.
Received on Thursday, 17 February 2000 13:33:23 GMT

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