5.6 Command and Control

Command and control systems analyse data in real-time and permit a `commander' to take appropriate action. In some cases, the system may propose courses of action, or even initiate a course of action. Examples of command and control are the management of a car's engine system, the management of nuclear reactors, ambulance dispatch, and the management of defence and attack systems in battle. In each case, the computer is used to rapidly analyse a complex and perhaps rapidly changing system and to assist in ensuring a `favourable' outcome (which may be increased engine performance, the avoidance of a core melt-down, optimizing the chances of patient survival by sending the nearest ambulance or the destruction of enemy forces).

Command and control systems are often amongst the most complex uses of computer systems, because of the sophisticated instrumentation often involved (for example, the analysis of satellite pictures of a battlefield), the need to account for physical attributes that may not be easily characterized (such as traffic congestion) and sometimes because of the short time allowed for analysis (in some situations, a control system must detect and recognize critical situations in a reactor in under ten seconds).

Command and control systems are often safety critical; that is, the consequences of a malfunction can be catastrophic: for example, it was alleged that dozens of deaths were caused by a faulty ambulance dispatch system. Consequently, command and control systems must often be designed to be fault-tolerant; for example, to include redundancy in case of equipment failure or to include failsafe systems in case of operator error. Fault-tolerance often adds to the complexity of systems.