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.<>