Defining that interface is the hard part of the job. But that is the difficulty.
Applets work by restricting permissions on certain threads.
Servlets work by restricting permissions on certain threadgroups, a model I don't like because it requires a thread for each servlet installed on a server even though many wouldn't otherwise require a thread. In Jigsaw, all resources are executed by Client threads. It strikes me as difficult without substantial changes in jigsaw architecture to preallocate threadgroups for client threads which correspond to the various permissions profiles that one might be maintaining. A lookup facility that enabled a SecurityManager to check which client thread was using which resource at any given moment could then return permissions for the particular resource. Out of curiosity, do you have some documentation that compares jigsaw to servlets so that I can better defend our decision to use it.