Generating modified 5.0 DTD using mods to RELAX NG version

I 
created an RNG schema modification file, as described at http://www.docbook.org/docs/howto/, 
and using jing I can validate a demo document against it. 

 

Next, 
I tried to create a DTD from my modification file using trang, but got 
a lot of errors. Even using trang to try to convert docbook-5.0\rng\docbook.rng 
with no reference to modifications, I get about 100 error messages. Most say 
'error: sorry, cannot handle this kind of "choice"', but many follow this 
format:

 

  
sorry, not handled: duplicate declaration of element "info" from namespace "http://docbook.org/ns/docbook"

 

Were 
the official distribution DTD versions created using an automated tool, and if 
so, which one? 

 

thanks,

 

Bob

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