Bob pointed out that the Requirements of the Control System are largely independent of the implementation approach, so it is not too early to look at the available technologies and understand the advantages and disadvantages of the currently visible alternatives. Many of these technologies may be very different at implementation time. The WEB is the client-server model of choice and the common denominator world wide.
Software methodologies revolve around distributed Objects and network protocols.
Objects can be defined and operated upon across all of the machines of the network and provide a wide range of services. Java may be becomming the better implementation with host platform independence and mobile code. Running Objects on top of a standard relationsal database will have performance issues for high data rate archivers and the like. Oracle recently provided facilities for very large databases ,which are segmented for access but appear to the task to be one big database. Other recent object oriented database products are also available and might meet our needs.