Modes in human-automation interaction: initial observations about a modeling approach

This paper is an exploration into the relationship between the operating environment and the mode-structure of supervisory control systems. Based on a field-study describing operators (e.g., pilots, controllers, technicians) interaction with modal systems, the authors developed several hypotheses about why and how operators transition among modes. The authors used these hypotheses to develop a framework of the complete environment-human-machine relationship. The framework, called 'OFAN', is based on Statecharts and Operator-Function models-both modern extensions to the finite-state-machine theory. Using the OFAN framework, the authors describe two examples of moding problems and identify the system's features that induce such problems. In the first example, a moding problem in a display, it was the product of dual transitions into a state: one consistent with the layout of the controls/displays (and therefore intuitive), the other dependent upon some internal state (and therefore unintuitive). In the second example, a moding problem in an automatic flight control system, it was a default entry into a state (of the machine) which was inconsistent with the state of the environment. For both examples, the underlying approach and methods used to highlight these moding problems are briefly discussed.