Documenting the design of safety-critical, user interfaces

A number of techniques have been developed to map out the ‘design space’ of interactive systems. For instance, design rationale notations represent the various options that must be considered during interface development. Such notations offer important benefits. For instance, they can be shown to regulatory authorities to demonstrate that sufficient attention has been paid to particular design issues. Unfortunately, these notations are semi-formal. This leads to a number of weaknesses. They cannot be used to determine whether criteria and options have been used consistently during the development of an interactive system. Nor do they provide any procedures to determine whether interface design decisions have indeed been guided by a rationale. These are important limitations when regulatory authorities, such as the UK Health and Safety Executive, expect designers to demonstrate the consistency and coherence of their decisions. This paper addresses these problems and shows how decision theory can be employed to support design rationale during the development of human-computer interfaces for safety-critical systems.