[NTG-context] hierarchical modes

Hello, I need to prepare a document for different audiences. The question here is, how to encapsulate the different parts of the document. There are paragraphs which are "public", some more which are "internal" and some which are "private". People who are in the private group should see everything, the group internal only the public parts and the internal ones. As far as I see, modes are not additive. What would be the best way to structure such a document and to style the different paragraphs, so that the different audiences see, who can read what? Thanks in advance, __Janko Hauser