Middleware in Accelerator and Telescope Control System

Middleware is an integral part of all modern control systems [1]. In the past the term middleware was used to refer to the first abstraction layer between the lower-level hardware access layer and the higher level application layer. It was often introduced to hide the network communication protocols. Middleware has developed far beyond this. Modern control systems can now have multiple middleware layers which take care of the network but also increasingly the modelling aspects of the control sytem. New middleware component models provide the technology for modelling the control system from the highest level down to the hardware access level. This paper will make a review of the current middleware situation in accelerator and telescope control systems. The main component models for CORBA, Java and .NET will be discussed. The paper will cover common network protocols like IIOP, RMI and SOAP and their use in control systems.