The device model of interaction

Any interactive system can be described in terms of the devices it involves, and their interconnections. Similarly, each device can be described in terms of simpler devices and their interconnections. Such descriptions are strictly modular, and well structured. This observation allows any system to be described, at all levels, by the same language. Such descriptions have intuitive appeal for hardware as well as software components, and for process control applications as well as human-machine interaction. The Device model of interaction, as described here, can ease the job of designing user- friendly interactive systems, and can be adapted for automatic compilation. As an example, the design of an actual system component is discussed. The design is presented, at several levels, in a Pascal-like notation. It represents a module created to provide a human-machine interface via a graphic tablet, keyboard and video monitor.