Protocols for process interaction

The timing effects of interactions between the component concurrent processes of a real-time system, and between these processes and the system environment, have a crucially important role to play in determining the temporal properties of the system as a whole. First, a new and comprehensive set of unidirectional protocols for characterisation of these timing effects is developed, based on interaction by means of data items shared between two processes. Each protocol is represented by a graphical symbol which denotes its functional and temporal properties, and axiomatic specifications for the protocols are derived which define and reveal their essential behaviour. The protocol set is then extended to include important bidirectional forms to allow for the remoting of interfaces, which is needed in distributed systems, and to support remote procedure call techniques. Protocol implementation takes the form of a connector known as a route. It is shown how routes can be combined and encapsulated within higher level constructs to give distributed interaction, and a sample algorithmic implementation of a route is given. The axiomatic specification technique is used to make comparisons with some more conventional forms of interaction. The paper brings new insights to the characterisation and realisation of connectors in distributed real-time systems.