[mdr-users] createExtent(String, RefObject, RefPackage[])

Hi all,
I'm looking for some information on the method to create an extent
that clusters an already existing extent:
(i.e. http://www.netbeans.org/download/dev/javadoc/MdrAPIs/org/netbeans/api/mdr/MDRepository.html#createExtent(java.lang.String,%20javax.jmi.reflect.RefObject,%20javax.jmi.reflect.RefPackage[])
)

A short explanation of the array argument or some example code should do it.  

I passed a one-size array containing a UML extent to it but the
clustered UML extent of my tracing extent (see
http://www.fots.ua.ac.be/motmot/docs/traceability-p3.php) remains
empty.  I already found it a bit weird that I didn't have to specify
in which package of the tracing extent the existing UML extent should
be loaded.  Sure, in my case there's only one clustered UML extent but
problems should arise as soon as there would be more... therefore I
must be missing something...

Thanks in advance,
-- Pieter.