Usability Evaluation Models - High Level Models and Methodologies for Information Systems - page 83

Fig. 5.2 Basic process of heuristic evaluation

5.5 Goals, Operators, Methods, and Selection Rules
(GOMS)

GOMS model was developed and invented by Card et al. ( 1983 ). This model aims
to present the knowledge of determined human computer interaction and how user
can interact with computers and the implications for designers. This model
endeavors to reduce the complexity in the interface as well as in the cognitive
resources and engineering. Under this model,

there are speci c elements that

describe purposeful HCI, illustrated in Table 5.1 .

Goals specify what the user wants and intend to achieve.

￿

Operators are the building blocks for describing human computer interaction at

￿ -

the concrete level.

Methods are sequences of sub-goals and operators to accomplish a goal.

￿

Selection rules predict which method will be used. For example, “ If the mouse is

￿

working, select ' point to an item on screen, ' if not select choose OPEN option in

file menu. ”

Finally, GOMS model is based on levels of interaction that bridge the gap
between the abstract (psychological) task and the concrete (Physical System).

Table 5.1 GOMS

Goals User needs

Operators HCI building blocks

Methods Programs built through operators

Selection rules De nition of what methods will be used