Reports from Working Groups: The Challenge of Time

In the past, temporal problems have not played a central role in the development of human-machine interfaces. The timing of individual commands seldom affects single users interacting with standalone applications, such as text-editors and spreadsheets. This situation is changing. The increasing use of mutlimedia applications, distributed systems, computer supported cooperative work tools and process control environments is forcing designers to consider temporal aspects of usability. It is a non-trivial task to synchronise the activities of multiple operators working through several different modalities on many different machines. Unfortunately, traditional techniques that rely upon rapid prototyping or iterative development cannot easily be used to address the many different timing issues that arise during the design of this new generation of interactive systems. In contrast, formal specification techniques provide concise and precise means of representing and reasoning about such interactive behaviour. This paper argues that existing notations are, however, poorly equipped to face the challenges posed by temporal aspects of usability.