Assessing Usability from Formal User - Interface

In this paper we demonstrate usability analysis of Object-Z user-interface designs. Usability can be deened in terms of ve salient properties of an interactive system: task eeciency, reuse, user-computer communication, robustness and exibility. Formal user-interface designs have been touted as a basis for determining the usability of an interactive system prior to the expense of system development. However to date, a comprehensive demonstration of the utility of formal designs for this purpose has not been forthcoming. We show that formal user-interface designs provide a valuable basis for usability analysis.