Hugo Simpson and Eric Campbell

Matra BAe Dynamics

The real-time network architecture represents a computing system in terms of a set of independently operating processing components which interact with each other and with their environment through a set of connection components. The connections notionally contain data which is shared by the connected processes but which is not owned by any of them. The shared data in a connection decouples the connected processes and so provides a form of asynchronous interface. A system can be modelled in this way from functional, design, distribution and execution viewpoints, thus ensuring that the asynchronous interface concept is exploited during all stages of system development from functional definition through to product fabrication.

A taxonomy of interaction protocols has been introduced which is built up by consideration of destructive and non destructive forms of reading and writing of shared data, and by varying the amount of such data that can be held in the connection element between processes. Each protocol has a distinctive symbol and name, and the protocols collectively characterise a range of dynamic constraints imposed by the shared data model of interaction. The protocol set covers many forms of bilateral interaction commonly found in practice. Protocols can be combined to give more complex effects, and there is a flexible and general form of interaction component to allow for effects not derivable from the defined set.

Real-time networks were originally proposed to deal with the development of complex real-time systems implemented in software executing on conventional microprocessors. More recently, substantial improvements to the approach have been achieved by the application of VLSI technology to the process scheduling and interaction mechanisms which are needed during network execution. Asynchronous hardware logic, together with a complementary set of software primitives, produces a compact form of micro kernel giving efficient and deterministic network operation in both single and multi processor systems.

The real-time network approach grows out of, and feeds into, real industrial applications. It places a special emphasis on distribution and timing aspects, and gives excellent traceability and management control throughout system development. It is supported by design tools and generic components which have demonstrated their value in terms of economic development and product robustness.