How to build a model programmatically ?

Hi everybody,
thanks a lot for your advice. Now I can handle my metaconcepts as I 
wanted to do.
But I still have a problem... When I try to write it in an xmi file (I 
just do the same thing as in the java code example posted by Antony), I 
get the following exceptions :



javax.jmi.reflect.InvalidCallException
	at 
org.netbeans.mdr.handlers.InstanceHandler.refGetValue(InstanceHandler.java:376)
	at org.netbeans.lib.jmi.xmi.WriterBase.writeReference(WriterBase.java:1044)
	at org.netbeans.lib.jmi.xmi.WriterBase.writeInstance(WriterBase.java:741)
	at org.netbeans.lib.jmi.xmi.WriterBase.writePackage(WriterBase.java:638)
	at org.netbeans.lib.jmi.xmi.WriterBase.writePackage(WriterBase.java:654)
	at org.netbeans.lib.jmi.xmi.WriterBase.writeDocument(WriterBase.java:551)
	at org.netbeans.lib.jmi.xmi.WriterBase.write(WriterBase.java:224)
	at org.netbeans.lib.jmi.xmi.WriterBase.write(WriterBase.java:195)
	at 
org.netbeans.lib.jmi.xmi.DelegatingWriter.write(DelegatingWriter.java:45)
	at org.netbeans.api.xmi.XMIWriter.write(XMIWriter.java:77)
	at MDRTest.main(MDRTest.java:84)



In the JMI specification, I can read that InvalidCallException are 
"Thrown by reflection methods when client tries to call them 
incorrectly. (e.g. when refSetValue is called for attribute which is not 
changeable)" (?!?!)
Is this problem frequent ? Do you have an idea ?

Regards, and thank you again for your advice.