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   RE: [xml-dev] Capitalism and XML (was RELAX NG Marketing)

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That sounds good and thanks, John.

Has anyone any prognostication of how this would work 
in the projected DSDL?  In other words, what kind of 
tools would that provide and what kinds of functionality?
If one starts with RNG, will the upgrade to DSDL be 

In short, what kinds of legacy problems are we looking 
at post-RNG and maybe post XSD?


From: John Cowan [mailto:jcowan@reutershealth.com]

"Bullard, Claude L (Len)" scripsit:

> 1.  More productive.  Can one compose faster, is it easier to learn, 
> does is do what I need to do in the framework?

Well, I'm a fairly bright sort of guy, and I could run RNG into my
rapidly aging brain with no trouble, but XSD (part 1) is still defeating

I would say that RNG is far and away the least restrictive schema
language of its type (excluding Schematron, Examplotron, Hook, etc.).
In essence, if you can write down RNG, and it makes any sense at all
(no elements within attributes or consecutive datatypes, e.g.) then it just
*works*, period.  It has three syntaxes: XML-instance, programming-language,
and DTD, for validators, schema authors, and legacy respectively.

Its main weakness as against XSD is that it has no key/keyref support
other that DTD-compatible ID, IDREF, and IDREFS (which are technically
an extension, but supported in the existing validators).  These were
present in earlier drafts, but were too messy and hard to get right
in the general case, and were dropped from RNG 1.0.  Identity
constraints are really orthogonal to structural ones in any case.
This is a job waiting for someone to have a brain-wave.

The spirit of RNG is closely related to that of DTDs: there is a smooth
mental upgrade path.  As a result, the DTD-RNG conversion tool is a masterpiece
of structure preservation: it does its very best to make whatever structuring
in the way of parameter entities that the DTD has, appear transparently
in the RNG as well.


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