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RE: Are we losing out because of grammars?

• From: "Bullard, Claude L (Len)" <clbullar@i...>
• To: xml-dev@l...
• Date: Thu, 01 Feb 2001 09:02:52 -0600

Ummm... so far it looks like they have about 
the same expressive power.  Can you show 
examples where they don't?  Appreciated...

One is sometimes struggling against the legacy,  
actually "the rules of now". For example, SGML 
exclusions and inclusions were used because 
the thing being modeled was itself, a document 
that a modeler might consider irrational on 
the surface.  Later, one found that the process 
or route of the document made that a requirement.  
One might have broken up the DTDs into multiple 
DTDs appropriate to different steps (and in very 
many cases should have; that was a political 
problem), but then one had to state authoritatively 
that these were different documents and sometimes, one 
was not allowed to redefine the artifacts that 
way.  Thus, we ended up with the ungainly but 
workable "switch DTDs" with ORs at the top 
level and occasionally scattered throughout 
to maintain wrapper tags.

It isn't simply rules vs grammar.  That is too 
easy an assumption.  It is also a problem 
of matching means to process and process 
to requirements.  

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...]

Smart readers of XML-DEV will of course say "oh, but probably you can
express things in
content models that you cannot express in paths and rules" but I have my
doubts: a really complex content model is IMHO often (always) either the
sign of struggling against the grammar or a kind of tag ommission: if there
is some complex structure there, why isn't it explicitly labelled for all
the world to see?

Cheers
Rick Jelliffe

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