[tei-council] Schematron extraction issues

[Syd Bauman]

I.
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As mentioned in a previous conversation between me & Sebastian,
extract-isosch.xsl still does not do the right thing for default
context of some constraints that are inside <classSpec>. 

Also we do not have @validUntil code for several constructs. These
are constructs we are not using @validUntil on (yet), so this is not
an urgent problem.

I've created bug 363 for these and assigned it to myself.

II.
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The extracted Schematron generates more than one <ns> which have the
same prefix and URI. I'm not sure, but I don't *think* this is a
violation of ISO/IEC 19757-3. And oXygen does not complaint. But
probatron complains mightily:
  FATAL java.lang.IllegalArgumentException: Cannot register a prefix
  or Namespace name that has already been registered

We've had this situation for years, but at some point perhaps we
should fix it. The only way I can see to do this is to add a complete
internal pipeline pass which end up flattening the two namespace
sections into one. (Currently, explicit ns copied from the input are
separate from implicit ones generated from the namespace nodes of the
input.) If someone sees a better way, let me know, or go ahead and
throw it in there.