ABSTRACT
Human functions have to be treated collectively, not singly, so that they are mutually compatible and can be amalgamated into jobs. Engineering concepts, mathematical concepts and computer concepts have all been enlisted to describe human–machine systems, and have seemed feasible in so far as they can accommodate times, events, probabilities, associations, dependencies, and error and failure rates. The employment of machine language and concepts to describe the human as a system component has seemed a matter of expediency rather than choice. The replacement of a human function by a machine function can have profound human consequences, yet seem a trivial change when expressed in system concepts. The process of allocating functions to human or machine seems attractive and logical. All information from the human to the machine and from the machine to the human must pass through the interface. The human–machine interface is open and observable in traditional air traffic control workspaces.
