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RE: Request for a poll: (was RE: Datatypes vs anarchy)

• From: "Bullard, Claude L (Len)" <clbullar@i...>
• To: Rick Jelliffe <ricko@a...>,Ronald Bourret <rpbourret@r...>, xml-dev <xml-dev@l...>
• Date: Thu, 15 Mar 2001 09:09:21 -0600

Urrp.  That is PRECISELY what bedevils X3D 
and it was brought up several times by 
different sources during the XML Schema work.
We did a long thread on the power and ways 
of groves as a result.  Henry says, 
"almost but not quite groves".  VRML has 
the problem of orignally defining the 
abstract node/fields in the same syntax 
as the actual instance language.  That 
made it difficult when the time came 
to add an XML syntax.  The problem can't 
be succinctly stated:

o  One abstract object model; multiple syntaxes. 

It has become madness and split the VRML 
efforts cleanly into multiple efforts 
(X3D, RM3D) and diverging models.

Why?  XML isn't just syntax.  It has an explicit 
element/attribute separation of namespace. 
Elements can have have attributes.  Attributes 
can't have elements as children.  VRML97 
has nodes/fields.  Children fields can 
have nodes.   Groves could handle that 
fine.  XML can't.   The bedevilment was 
to make a clean map, we needed the 
wrapper elements to emulate some of 
the fields (eg, children).  To an 
XMLer, it looks silly because XML 
doesn't need those.

So what you are suggesting looks right, 
but I contend we are just going right 
back down the same path the groves 
guys went down.  Nodes is nodes, 
properties is properties, someone 
chooses names.

Len Bullard
Intergraph Public Safety
clbullar@i...
http://www.mp3.com/LenBullard

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


-----Original Message-----
From: Rick Jelliffe [mailto:ricko@a...]

Yes. And there is a nice design issue here for the future too:

Perhaps what we need for a schema language is something along the lines of
  <schema>
     <conceptual-model>
    ...
     </conceptual-model>
     <language-binding>
    ...
     </language-binding>
  </schema>

In XML Schemas, we have found all sorts of nice abstractions (components)
for what goes on in a language.  Yet the conceptual modeling people (I think
Robin Cover and Peter Chen might concur) think that the bottom-up approach
is odorous.

That is why, to jump on my hobbey-horse, I don't see that we need more
grammar-based schema languages (not to say that we shouldn't continue to
perfect and mate existing ones).  Instead, we need to start thinking about
what schema languages would be needed to implement the above kind of schema.

Personally, I think that a schema language made from ER for the conceptual
model and a Schematron-like language to do the language binding might be a
nice fit (if Schematron-like languages can be extended to act generatively.)

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