Synchronization Expressed in Types of Communication Channels

                          Franz Puntigam
    Institut für Computersprachen, Technische Universität Wien
           Argentinierstraße 8, A-1040 Vienna, Austria
             E-mail: franz@complang.tuwien.ac.at

Static typing and subtyping are useful concepts in object-oriented
programming languages. Unfortunately, current type models for concurrent
object-oriented languages are not yet as expressive as they should be:
Clients have to rely on synchronization behavior not expressed in the
objects' types. In the type model proposed in this paper, types of
communication channels make synchronization constraints explicit. Static
type-checking ensures that messages are sent only if the receivers can
deal with the messages at the time when they are received, although the
set of accepted messages can change dynamically.