MAP-01-011 HFI Technical Guide - Human Factors Integration ...

Annex 3 – HF Techniques, Methods and Tools• Disadvantages• The reliability and validity of the technique is questionable.• Observation data is often flawed by a number of biases.• When used predicatively, timeline analysis can only model error freeperformance.• Initial data collection phase is time consuming and resource intensive.A3.4.6Goals, Operators, Methods and Selection Rules TechniqueThe Goals, Operators, Methods and Selection Rules (GOMS) technique is part ofa family of HCI orientated techniques that is used to provide a description ofhuman performance in terms of the user’s goals, operators, methods andselection rules. GOMS attempts to define the user’s goals, decompose thesegoals into sub-goals and demonstrate how the goals are achieved through userinteraction. GOMS can be used to provide a description of how a user performsa task, to predict performance times and to predict human learning. Whilst theGOMS techniques are most commonly used for the evaluation of existingdesigns or systems, it is also feasible that they could be used to inform thedesign process, particularly to determine the impact of a design on the user.The GOMS technique is based upon the assumption that the user’s interactionwith a computer is similar to solving problems. Problems are broken down intosub-problems, and these sub-problems are broken down further. Four basiccomponents of human interaction are used within the GOMS technique. Theseare defined below:1. Goals – The goal represents exactly what the user wishes to achievethrough the interaction. The goals are decomposed until an appropriatestopping point is achieved.2. Operators – The operators are the motor or cognitive actions that the userperforms during the interaction. The goals are achieved throughperforming the operators.3. Methods – The methods describe the user’s procedures for accomplishingthe goals in terms of operators and sub-goals. Often there are more thanone set of methods available to the user.4. Selection Rules – When there is more than one method for achieving agoal available to a user, selection rules highlight which of the availablemethods should be used.• Advantages• GOMS can be used to provide a hierarchical description of task activity.• The methods part of a GOMS analysis allows the analyst to describe anumber of different potential task routes.May 2006 Page A3-33 Issue 4