iptors 
  as control metadata to represent the available files; files themselves may be added, 
  modified, and downloaded through FileSubscriber and FilePublisher.
  
  <p>
  The FileManager keeps files in "groups," with permissions settable on a per-group basis. 
  Users with the owner role are able to add, modify, and delete these groups. By default, 
  only users with a publisher role and higher may publish a file to a group, while those with
  role of viewer or higher are able to download.</p>
  
  <p>