1 . WHAT IS SYSTEMS ENGINEERING ? The Development of Systems Engineering RICHARD

0018-9251/84/0700-0306 $1.00 ) 1984 IEEE Systems engineering is the design of the whole as distinguished from the design of the parts. The systems engineer harmonizes optimally an ensemble of subsystems and components-machines, communication networks, humans, space-all related by channeled flows of information, mass, and energy. Of course, the designer of a chair, a watch, or even a necktie deals in the end with the whole; so, in a sense, every designer is partially a systems engineer. But where that whole has many components and many complicated interactions occur when they are connected, real systems engineering is required. Then systems engineering becomes a demanding intellectual discipline. In complex systems, the large interactions will often dominate, but equally often a surprisingly large accumulation of individually small factors will exert tremendous influence on performance. A large system with many parts, each of which appears to be adequately accurate, may turn out to produce unacceptably inaccurate overall results. In a similar way, a system of many apparently reliable parts may add up to an unreliable system. Again, many feedback loops may be necessary in a system, but their presence also may produce unexpected phenomena far from what the designer intended. These and other system characteristics make systems engineering a challenge.