Analysing complex tasks with an extended GOMS model

To analyse more complex tasks of human-computer interaction the original GOMS model of Card, Moran and Newell (1983) is extended by adopting the concept of propositional terms for goals and operations. The control structure of GOMS is refined and the concepts of schemata and units are introduced to examine consistency and learning with the extended GOMS model, additionally. The task of academic scheduling is used to demonstrate the power of the extended model. By means of the results from an empirical investigation it is pointed out how to predict performance using GOMS*. Finally, it is discussed how to analyse errors and how to derive hypotheses for constructing help systems from a GOMS* description.