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Re: [xml-dev] The task to be solved by RDDL. Re: [xml-dev]RDDL(was RE: [xml-dev] Negotiate Out The Noise)

From: Elliotte Rusty Harold <elharo@-------.---.--->
To: xml-dev@-----.---.---
Date: 1/21/2002 3:53:00 PM
At 10:31 PM -0800 1/20/02, Paul Prescod wrote:
>Elliotte Rusty Harold wrote:


>The RDDL spec. says: 'An example of a "class of resources" is that
>defined by an XML Namespace.' but the XML Namespaces specification does
>not use the word "resource" (other than in URI). Much less does it
>discuss "classes of resources."
>

Now that I think about it a little more, I'm not absolutely sure a 
RDDL document shouldn't be used for document metadata, as opposed to 
namespace metadata. It just isn't used that way now. The RDDL spec is 
flexible enough to support that use. However, a new convention for 
associating RDDL documents with documents would be needed since we 
could no longer rely on just the unique RDDL document at each 
namespace URI.

>Consider an XSLT or SOAP document with embedded XHTML. You would not
>expect to validate this document by using a schema for the containing
>vocabulary and switching to a schema for the contained vocabulary
>mid-stream. That typically would not work because the container controls
>the interpretation of the contained data to such an extent that the
>schema may not fit anymore.

I'd argue that's a problem with the schema language and or specific 
schemas that were written without taking this into account, and has 
little to do with RDDL.

>  Or maybe there is a schema that is
>appropriate for validation in an XSLT or SOAP context -- but how would
>you find it in a RDDL document?
>

Easy:

<rddl:resource xlink:href="http://www.example.com/myappinsopa.xsd"
   xlink:role="http://www.w3.org/2001/XMLSchema"
   xlink:arcrole="http://www.exxample.com/purposes/soap-schema-validation"
/>


>In a closed system, I can set up RDDL's so that they have exactly the
>right set of schemas and stylesheet fragments to make all of my
>namespaces work together. Maybe I actually enhance the schemas and
>stylesheets provided by a namespace maintainer instead of using them out
>of the box. But if we all share schemas through RDDL URLs then the
>chances of the schemas working together are slim. And if the system is
>unreliable in general,


Please don't blame RDDL for the fragility of existing schema 
languages. RDDL can list all the schemas, and it can say which ones 
are used for what, but it can't make them cooperate if the schema 
designers don't want them to.
-- 

+-----------------------+------------------------+-------------------+
| Elliotte Rusty Harold | elharo@m... | Writer/Programmer |
+-----------------------+------------------------+-------------------+
|          The XML Bible, 2nd Edition (Hungry Minds, 2001)           |
|              http://www.ibiblio.org/xml/books/bible2/              |
|   http://www.amazon.com/exec/obidos/ISBN=0764547607/cafeaulaitA/   |
+----------------------------------+---------------------------------+
|  Read Cafe au Lait for Java News:  http://www.cafeaulait.org/      |
|  Read Cafe con Leche for XML News: http://www.ibiblio.org/xml/     |
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