[mdr-users] How I can create an Extent ?

Hello,

I started with NetBeans trying to follow the "Example of Using NetBeans" 
(http://mdr.netbeans.org/example.html).

Now, I have the interfaces according to the example metamodel.
However, I'm trying to compile and execute the code of the example for 
accessing to metadata and I have some doubts :

Basically, my problem is that the operation getExtent() always return null.
I think that I  can't understant very well what an "Extent" is.

Therefore I would like to know what steps I can follow in order to :

"Create a new instance of "Project" package in "Project model" extent 
and name it "Projects metadata" (so that repository.getExtent("Projects 
metadata") call in the example above does not return null)."

Can I create it using NetBeansExplorer ?

Thanks