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   RE: XML Schemas: Best Practices

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  • From: "Bullard, Claude L (Len)" <clbullar@ingr.com>
  • To: "Roger L. Costello" <costello@mitre.org>, xml-dev@lists.xml.org
  • Date: Fri, 22 Sep 2000 10:49:57 -0500

I very much appreciate this thread, Roger. 
Useful to all of us. Some thoughts:

One can always flatten out the namespace 
by dynamically creating a schema.  Here are 
some speculations about where and when 
one might want to know the namespace:

1 A namespace on the element indicates a 
a variant or version of the element.  For 
example, when managing vocabularies where 
the application language is aggregate but 
uses separately developed sub-schemas .

2.  A namespace on the element is used 
to infer the handler.   This is probably 
a weak reason unless one is also in effect but 
extensibility by components is how server-side 
systems work.


3. The schema is going to be a dynamic 
object in the authoring process, that is, 
multiple authors working in each language 
create a work that must be schema-validatible 
but the process itself requires traceability.  
The schema is created just prior to sending 
the document.  I might want this to help with 
number two so I can figure out the packages 
to be delivered with the work or that must 
be available, ie, part of the dllHell solution 
particularly in distributed development teams.

4.  An extension of traceability but a separate 
issue is authority.  For example, a language 
may be aggregatible but the instance is proprietary.  
Consider a solution where copyright ownership is 
associated to a namespace identifier.   That is, 
the owner of the namespace as signified by the 
URI is also the owner of the copyright and asserts 
this using the URI.  As with 3, the authors may 
want to maintain separate ownership when contributing 
to a jointly developed complex work.

Len Bullard
Intergraph Public Safety

Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h

-----Original Message-----
From: Roger L. Costello [mailto:costello@mitre.org]

Now it is time to answer the question: what characterizes systems for
which it makes sense to design the schema so that instance documents are
forced to display the namespaces for each element?  

One quick answer is:

"For systems where knowledge of the namespaces DOES provide additional
information design the schema to force exposure of namespaces in
instance documents."

However, this leaves me a bit empty.  When does "knowledge of the
namespaces provide additional information"?  That is the question which
must be answered. 


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