Joachim Schrod writes:
 > Do you really want to tell us that TEI is not one of the most complex
 > DTDs that ever got written?
no. but its used quite a lot.

 >  Docbook is not an easily understandable one, either.
plenty of people seem to manage with it

 > Could you please bring in other examples? These currently support the
 > hypothesis that it's "tortuosly difficult".
the fact that Docbook and TEI are themselves complex does not
demonstrate that the extensibiliy features were/are hard to add.

no, i dont have any other convincing examples. but if i asked you to
develop a DTD, and said I wanted some extensibility, you would say
"sure, no problem, lets see what you need", i bet.