I'm working in a situation where I have read-only access to an existing database, and using NH to load data from that, with read-write access to another database and using NH to read and write from that DB.
The RO-database has an entity "Foo" which has a many-to-many relationship with "Bar" ... I have set the mappings for both entities to SchemaAction.None, but NH still exports the relationship table during SchemaExport.