Coordination of CORBA Objects with Process

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

Coordination is one of the most important tasks in concurrent,
distributed program development.  Conventional interface definitions
like the CORBA-IDL do not support the programmer concerning
coordination. Messages sent at the wrong time may cause errors to
occur at remote sites, where they are difficult to handle.  Much
design effort is required to avoid them. Process types provide means
to ensure that all clients are coordinated before sending a message to
a server so that no message-not-understood-errors can occur even
if the understandability of messages depends on the server's state.
An extension of the CORBA-IDL allows us to combine the benefits of
process types with the basic object design of CORBA. Type errors
caused by wrong message orderings are detected at run time before
these messages are sent to a remote client; the exceptions can be
handled locally.  A subtyping relation allows us to inherit
restrictions on message orderings.