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Re: RDF and RDFS Schemas?

From: Shawn Bowers <sbowers@ucdavis.edu>
Date: Wed, 12 Jan 2005 13:35:32 -0800
Message-ID: <41E59824.9000307@ucdavis.edu>
To: Sandro Hawke <sandro@w3.org>
CC: "Burkett, Bill" <WBurkett@modulant.com>, www-rdf-interest@w3.org

Sandro Hawke wrote:
>>I'd like to hand-build some RDF/RDFS test cases using an XML Editor =
>>(e.g., XMLSpy) but - much to my surprise - I haven't been able to find =
>>an XML Schema (or even a DTD) for either of these.  (Or nothing recent =
>>anyway - I found "attempts" at creating XML Schemas for RDF but they're =
>>all over 5 years old.) =20
>>
>>My first question is: Does anybody have, or know where I can locate, an =
>>XML Schema (or DTD) for RDF and RDFS (and perhaps OWL)?  My second =
>>question is more general: why is it so difficult to find these things?  =
>>I would think they'd be available on W3.org smack-dab in the middle of =
>>the RDF project material where they'd be easy to find.
> 
> 
> The short answer is that it's not possible to make an XML Schema or
> DTD for RDF in general.  I'm not sure how to explain why not, but it
> may be clear if you think about how RDF/XML doesn't constrain much;
> almost any XML inside an rdf:RDF element is valid RDF/XML.   So a DTD
> wouldn't help much, even if one could be written.

I believe one answer is that when you define a triple, you can use the 
property of the triple (like "editor") as a tag name in the RDF/XML 
encoding.

For example, (taken from the RDF syntax and grammar spec):

<rdf:Description rdf:about="http://www.w3.org/TR/rdf-syntax-grammar">
   <ex:editor>
     <rdf:Description>
       <ex:homePage>
         <rdf:Description rdf:about="http://purl.org/net/dajobe/">
         </rdf:Description>
       </ex:homePage>
     </rdf:Description>
   </ex:editor>
</rdf:Description>

Here, "editor" and "homePage" are application-specific properties 
(perhaps defined in an RDF Schema), whereas "Description" is an RDF 
construct (i.e., "Description" would be an element defined in an XML 
Schema for the RDF/XML encoding).   You can basically use any property 
name you want in an RDF document (so long as it is a valid xml tag 
name), thus making it difficult to specify an accurate XML Schema and/or 
DTD for the RDF/XML encoding.

Shawn


> 
> Try looking instead for "RDF Authoring Tools" and see if you have
> better luck.
> 
>       -- sandro
Received on Thursday, 13 January 2005 03:07:44 GMT

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