Formal methods and iterative design

Formal methods allow a system designer to describe precisely how the system will be. In the area of human-computer interaction this means describing the structure and detail of the user interface. Giving the designer tools to think clearly about the decisions made must be helpful. However, the problem of deciding how the user interface is to be designed remains. In particular, to use such tools effectively a designer must have a good understanding of how the users think about the task, what their expectations and priorities are. This kind of information is best obtained by user testing with prototypes. An initial design is put forward and then refined using feedback from typical users doing typical tasks with a prototype. This refinement should happen in parallel with the refinement of a formal model of the user interface by the application of domain independent principles. In the early stages the cost of this procedure can be minimised by using simulations and mock ups rather than full prototypes. This is known as iterative design. This paper describes, through an example, some techniques which can be used to get insights about how a user approaches a task and the difficulties they have with a particular prototype