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