Using structural descriptions of interfaces to automate the modelling of user cognition

One approach to user modelling (Barnard et al., 1988) involves building approximate descriptions of the cognitive activity underlying task performance in human-computer interactions. This approach does not aim to simulate exactly what is going on in the user's head, but to capture the salient features of their cognitive processing. The technique requires several sets of production rules. One set maps from a real-world description of an interface design to an internal theoretical description. Other rules elaborate the theoretical description, while further rules map from the theoretical description to properties of user behaviour. This paper is concerned primarily with the first type of rule, for mapping from interface descriptions to theoretical description of cognitive activity. Here we show how structural descriptions of interface designs can be used to model user tasks, visual interface objects and screen layouts. Included in our treatment are some indications of how properties of cognitive activity and their behavioural consequences can be inferred from such structural descriptions. An expert system implementation of the modelling technique has been developed, and its structure is described, together with some examples of its use in the evaluation of HCI design scenarios.