Editing GOMS (section)

==Overview==
[[File:Elements of a GOMS model.svg|thumb|The concepts behind a GOMS model and their relationships]]
A '''GOMS''' model is composed of methods that are used to achieve specific goals. These methods are then composed of operators at the lowest level. The operators are specific steps that a user performs and are assigned a specific execution time. If a goal can be achieved by more than one method, then selection rules are used to determine the method.

* '''Goals''' are symbolic structures that define a state of affairs to be achieved and determinate a set of possible methods by which it may be accomplished
* '''Operators''' are elementary perceptual, motor or cognitive acts, whose execution is necessary to change any aspect of the user's mental state or to affect the task environment
* '''Methods''' describe a procedure for accomplishing a goal
* '''Selection Rules''' are needed when a goal is attempted, there may be more than one method available to the user to accomplish it.

There are several different GOMS variations which allow for different aspects of an interface to be accurately studied and predicted. For all of the variants, the definitions of the major concepts are the same. There is some flexibility for the designer's/analyst's definition of all of the entities. For instance, an operator in one method may be a goal in a different method. The level of granularity is adjusted to capture what the particular evaluator is examining.
For a simple applied example see [[#CMN-GOMS|CMN-GOMS]].