Thank you for your reply. You are right, maybe I have not expressed my position clear enough as I wrote this in a very rush. Moreover you are right, I am talking about AC23.
To come back to the question, I am quite familiar with the IFC Schema and how it works. Actually my question was pretty specific, so please let me know than if you know how to deal with it as I have not seen an option to do this - but maybe it was just a bit to hidden for me.
Your help is much appreciated,