The Star, a dynamically configured dataflow director for realtime control

The CEBAF accelerator is controlled by an automated system consisting of 50 computers connected to machine hardware and another 20 to 30 computers used for displaying machine data. The control system communication software must manage the inter-machine communication of these computers. Each of the different segments of software that make up the machine control system is treated as data sources and data sinks, with a single process mediating the transfer of all data between any data source/data sink pair. The mediating process is called the Star. This dynamically configured process keeps track of all available machine data posted by data sources and of all data requested by data sinks. Data transmission rates through the Star are kept low by sending only data that is requested by other control software, and then only when the value of the data changes. The system is entirely response-driven, with the Star process taking action only at the request of either a data source or a sink. The software for the communication is written using standard C code and TCP/IP sockets, making the communication software platform independent