We try to make an (incomplete) outline of Estelle mechanisms that have been discussed over last years. We think it is time to summarise some of the experience and be prepared for broader discussion on the language futures. We repeat and remind some arguments that were raised while the language was being designed, add some new ones and give references to works that addressed a particular subject. The mechanisms that are discussed below are not ordered by any priorities, and many of them are strongly inter-related. The list is by no means complete. We try to avoid any conclusive remarks, but our preference is to keep the original principles and "logic" of the language. We are making, however, some concrete proposition related to inter-module communication and structuralization.
Also, it should be stressed that we opt for a clear separation of purely specification (language) problems from (very important) problems concerning implementation and its efficiency. The latter are not treated here.
Only some of the mechanisms outlined below will be discussed deeply.