inheritance xml schema

My name is Nathalia Widjaya and I am Monash University student in Australia 
that is currently doing research degree in XML field. I have questions 
regarding this. Someone  wrote that XML Schema lack of multiple 
inheritance. Is it still like that until now? BUt, can we do it by mixing 
the hierarchy and attributes? How about the other types of inheritance, 
such as union inheritance, partition and mutual exclusive? If you know how 
to write that by example, could you please tell me how to do that? It will 
be much appreciated.

And, do you think XML schema can make the parent class in inheritance 
abstract...or disabled so that it can not be used in the XML to record the 
data...
  And, can we make the ID in the parent class as a sequence number so that 
the sub class will not overlap each other? Because what I am trying to do 
is to find out whether XML schema can support union , partial and mutual 
exclusive inheritance...and it requires the parent class abstract and the 
others requires the child class to be overlapped.

Thanks for your help.




~A life spent in making mistakes is not only more honorable but more
useful than a life spent doing nothing.~
Ralph Waldo Emerson

Cheers,
Nathalia Devina Widjaya