Goals, Operators, Methods, and Selection Rules

Acronym: 
GOMS
Description: 

Goals, operators, methods, and selection rules is a method derived from human-computer interaction (HCI) and constructs a description of human performance. The level of granularity will vary based on the needs of the analysis.

The goal is what the user wants to accomplish.
The operator is what the user does to accomplish the goal.
The method is a series of operators that are used to accomplish the goal.
Selection rules are used if there are multiple methods, to determine how one was selected over the others.

Uses: 

When analyzing existing designs.

To describe how a user completes a task. Allows analysts to estimate performance times and predict how the users will learn.

How do I use this tool?: 

1. DEFINE THE USER’S TOP-LEVEL GOALS.

2. GOAL DECOMPOSITION. Break down each top-level goal into its own subgoals.

3. DETERMINE AND DESCRIBE OPERATORS. Find out what actions are done by the user to complete each subgoal from step 2. These are the operators.

4. DETERMINE AND DESCRIBE METHODS. Determine the series of operators that can be used to achieve the goal. Determine if there are multiple methods and record them all.

5. DESCRIBE SELECTION RULES. If more than one method is found in step 4, then the selection rules, or which method the user will typically used, should be defined for the goal.

Expertise Required: 
This tool is an advanced tool and requires formal training or education.
Advantages: 

Methods portion of the GOMS analysis facilitates the description of numerous potential task paths.

Because GOMS allows performance times and learning times to be estimated, the analysis is able to assist designers in choosing one of multiple systems.

Provides hierarchical task description for a specific activity.

Disadvantages: 

Is difficult to use and complex compared to other task analysis methods.

Does not consider context.

Is mostly limited to the HCI domain.

Is time consuming.

Requires significant training.

Where can I go to learn more?: 

Stanton N, Salmon P, Walker G, et al. Task analysis methods. Human factors methods: a practical guide for engineering and design. Great Britain: Ashgate; 2005. p. 45-76.