ABSTRACT

Some products are designed to be useful with little or no human intervention. Examples of such products are such widely diverse devices as space satellites and residential furnaces. The device at each end of this spectrum must have been designed by engineers, it must have been fabricated and assembled, in the case of a furnace it must have been installed, whereas the satellite was mounted on a launch vehicle and placed into orbit, but once these events have occurred, there is only infrequent interaction—sometimes never—between the device and a human being.