using mdr api

Hello

I would like to use the MDR API to create and manipulate a model in 
memory without generating any code.
eg where is the javadoc I could read to know how to create a new 
metaclass directly in my ModelExtent.
I would need as well to read or modify an existing ModelExtent.


for instance :

MDRepository repository = MDRManager.getDefault().getDefaultRepository();

ModelPackage ModelExtent = (ModelPackage) 
repository.createExtent(ModelFile);

// add packages, classes, operations, attributes, tagged values, 
stereotypes ... in my ModelExtent

XMIWriter xmiWriter = XMIWriterFactory.getDefault().createXMIWriter ();

xmiWriter.write (System.out, ModelExtent, "");

thanks for further help

Julien Pla