NGOMSL

Overview

Natural GOMS Language technique was developed by David Kieras in 1988. The motivation was to make GOMS/CCT (cognitive complexity theory) simple to use, and still keep the power and flexibility of standard GOMS. This was necessary because GOMS did not have very well defined semantics. This lack of definition meant that two equally competent evaluators could do evaluations on the same system and come up with very different results. Kieras's result was the development of high-level (natural language) syntax for GOMS representation with directions for doing a GOMS evaluation. The recipe is referred to as a "top-down, breadth-first" expansion. The user's high-level goals are unfolded until only operators remain. Generally operators are considered to be keystroke-level operations, but that is not a rigid requirement.

Since NGOMSL is based on CCT, it has certain properties that make it unique. NGOMSL inherits the ability to not only give estimations for execution times but it can also estimate the time taken to learn how to use the system. It also, however, shares one of the major disadvantages all of the previous methods. NGOMSL models user interaction as a serial operation. One operation occupies the user completely, there is no multitasking, which makes NGOMSL inappropriate for analyzing tasks where the users are under time pressure, highly practiced and, in reality, do act in a parallel fashion.

Example

Goal: Move a file into a subfolder in Windows XP

Method for accomplishing goal of moving a file using the drag and drop option:

Step 1: Locate the icon of the source file on the screen Step 2: Move mouse over the icon of the source file Step 3: Press and keep holding the left mouse button Step 4: Locate the icon of the destination folder on the screen Step 5: Move mouse over the icon of the destination folder Step 6: Release left mouse button Step 7: Return with goal accomplished

Method for accomplishing goal of moving a file using the cut and paste option:

Step 1: Recall that the first command is called "cut" Step 2: Recall that the command "cut" is in the right click menu Step 3: Locate the icon of the source file on the screen Step 4: Accomplish the goal of selecting and executing the "cut" command Step 5: Recall that the next command is called "paste" Step 6: Recall that the command "paste" is in the right click menu Step 7: Locate the icon of the destination folder on the screen Step 8: Double click with left mouse button Step 9: Locate empty spot on screen Step 10: Move mouse to the empty spot Step 11: Accomplish the goal of selecting and executing the "paste" command Step 12: Return with goal accomplished

Selection rule set for goal: Move a file into a subfolder in Windows XP

If custom icon arrangement is used Then If no custom icon arrangement is used Then

Return with goal accomplished.