An HCI task analysis method that reduces a user’s interaction to its most basic actions. Operators (steps that a user performs) combine to form Methods, which are used to achieve Goals. Selection Rules determine the proper Method, when more than one could be used.
Quantitatively, GOMS gives good predictions of performance time and learning. Qualitatively, a GOMS model is a description of the knowledge needed to perform a given task, essentially describing the content needed for task-oriented documentation.
The late Jef Raskin describes GOMS in Chapter 4 of his book The Humane Interface.