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RE: RDF and RDFS Schemas?

From: Burkett, Bill <WBurkett@modulant.com>
Date: Fri, 14 Jan 2005 10:49:28 -0800
Message-ID: <3382A9E6F81014489B9F7A75960D98E801903C@lb1ex1.pdit.int>
To: <www-rdf-interest@w3.org>

Thanks, Sandro, Shawn, Dan for your responses.

Okay - I think I understand why there is no schema for RDF.  Would it be reasonable to say that RDF is more-or-less a syntax/grammar of a "instance" document?  Which is why there is a need for RDFS?  

If this is a case, I'd still like to find an XML Schema (not a Relax NG schema) for RDFS so I can create an RDFS schema to govern an RDF instance document (no one mentioned this in their responses).  Does anyone have any idea where I could find one?  My goal is to create an RDFS Schema to govern the hand-creation of RDF instance files (in an RDF editor or a plain old XML Editor that I can load the RDFS schema into) that I would like to use as test cases.  

(What I find so challenging about this discussion what I percieve to be as a casual attitude with respect to the boundary between "schema" and "instance".  I find that if I don't respect this boundary I find the discussions quite confusing.)

Thanks - Bill



> -----Original Message-----
> From: Shawn Bowers [mailto:sbowers@ucdavis.edu]
> Sent: Wednesday, January 12, 2005 1:36 PM
> To: Sandro Hawke
> Cc: Burkett, Bill; www-rdf-interest@w3.org
> Subject: Re: RDF and RDFS Schemas?
> 
> 
> 
> 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 Friday, 14 January 2005 18:49:59 GMT

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