RE: schema composition questions

 > Of course, there are plenty more other examples to cook up which are, at
least for me, similarly unclear.

 > I hope that you and the other experts here can help me out. 
 
All I can really say is that anyone who has tried to implement the spec has
found similar ambiguities. There are quite a few open bugs on the spec in
this area, and there are no definitive answers as to how corner cases should
work.
 
Michael Kay
http://www.saxonica.com/