Reflections on icons

This paper discusses the design of icons as tools for improving visual interface usability. No common accepted definition of `usability´ exists: hence we operationally define it in terms of a number of operator´s goals. We next derive the constraints and requirements necessary for achieving such usability, including both the designer and the user´s points of view as widely claimed in the technical literature. In this framework a new definition of icon is introduced. This definition is effective and has been embodied in a working prototype system, iteratively refined, illustrating the concepts discussed. We finally show how the definition affects the interface architecture as well as the required programming techniques