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   RE: XSchema Question 1: RDF

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  • From: "Simon St.Laurent" <SimonStL@classic.msn.com>
  • To: "Xml-Dev (E-mail)" <xml-dev@ic.ac.uk>
  • Date: Mon, 1 Jun 98 22:02:57 UT

We need to get the RDF discussion moving again so we can move on to specific 
syntax.  Dan Brickley suggested that I take a look at the W3C's P3P proposal 
for one example of how RDF/XML specifications can look like plain old XML 
without incurring much pain.  (I also hope he'll feel free to kick me if I get 
this discussion wrong.  Everyone else is welcome to join in as well.)

The proposal is at http://www.w3.org/TR/WD-P3P10-syntax.  Like nearly all of 
the W3C documents we're discussing here, this is a _Working Draft_, not a 
final spec, and is subject to change.

In the introduction, the authors specify:

>P3P uses  RDF/XML for the exchange of structured data and assertions.

The RDF/XML usage is a little strange, but later, in section 4.2, the 
relationship (to RDF and namespaces as well) is somewhat better defined:

>The following RDF captures the information as expressed 
>above. P3P proposals MUST be statements that are properly
>expressed according to the syntax model of RDF as well as 
>valid and well-formed XML. As a specific application of RDF we
>make a number of assumptions about RDF: 
>   1.the <RDF:RDF> tag may be optionally omitted. 
>   2.a tag without a name space should be assumed 
>      to be of the P3P namespace. 

P3P proposals are XML documents, and apart from the optional <RDF:RDF> tag, it 
isn't clear that there's anything fundamentally different about them.  
Sections 4.2.1-4.2.4 define elements used in P3P, using ordinary XML element 
and attribute terminology and no further discussion of RDF.

Appendix 3 provides non-normative DTDs for P3P XML, supplementing the ABNF 
used in the rest of the document.

This suggests that at least RDF doesn't have to make the spec unreadable or 

It still doesn't answer the questions of whether RDF is 
* Stable
* Understandable by enough people for this group to work with it
* Well-suited to this kind of schema creation.

Unfortunately, I'm not really qualified to answer those questions.  What I'd 
like to do is have us go ahead with creating XSchemas in XML, with the 
RDF-literate guiding development when necessary to keep us from landing on the 

That still leaves open the question of whether there are enough RDF-literate 
people out there, and whether they have time for such an adventure.  Comments? 
Suggestions? Volunteers?

Simon St.Laurent
Dynamic HTML: A Primer / XML: A Primer / Cookies

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