Hi Sayan,
many thanks for the answer. I saw as well your blogs. Indeed I have to retrieve the value from a specific attribute of context node BTCUSTOMERH or BTAdminH, but within the context node BTSUBJECT.
I have tried what you said but eventually I have to write code in the method GET of my attribute A1, (coming back to your example). In order to do that I have to invoke the component controller.
But unfortunately I am not able to initialize the component controller in order to retrieve my context node. So I got the above DUMP.
Anyway I thank you for the idea.
Regards.
Andrea