Keystroke-Level-Model
KLM (or KLM-GOMS) stands for Keystroke-Level Model, a hard science approach to human–computer interaction (HCI), based on CMN-GOMS, developed by Card, Moran & Newell, and spelled out in their book The Psychology of Human Computer Interaction, 1983.
It is designed to be easier to use than other GOMS methods, such that companies who cannot afford human–computer interaction specialists can use it.
How does it work
The KLM-GOMS model is designed to be as straightforward as possible. The sequence of operations is modeled as a sequence of a small number of operations. Each operation is assigned a duration, which is intended to model the average amount of time an experienced user would take to perform it.
Kieras (1993, 2001) defines the following operations:
- K, key press and release (keyboard) - 0.28 sec
- P, point the mouse to something - 1.1 sec
- B, button press or release (mouse) - 0.1 sec
- H, hands movement from mouse to keyboard or reverse - 0.4 sec
- M, mental thinking - 1.2 sec
- W(t), wait time (system) - t msec
A mouse click would be written "BB" (button press, button release) while a sequence of keys is "KKK..." or "T(n)" ("T" stands for "type").
A common operation that involves pointing and clicking something on the screen would be written "MPBB" (think, point, press, release).
KLM is not the only technique for evaluating interfaces, but it can be used to compare the speed of two different interfaces designed to accomplish the same task.
Problems with this model
This method assumes that operator times are invariant and do not depend on the previous sequence of events. New physical operators can be added if their timing can be represented as a simple context-free function. KLM-GOMS does not account for either slips or mistakes automatically -- the analyst must create separate models of error sequences and perform their own sensitivity analysis.
The placement of the keystrokes and pointer operations are straightforward, but the placement of the mental operations is not. Mental operations are placed by a set of rules that require some interpretation, such as determining a conceptual "cognitive unit" or grouping of actions. For instance, pressing ctrl and c simultaneously to perform a "copy" would be considered a single cognitive unit. Mental operations are inserted before each cognitive unit to account for cognitive preparation and decision-making.
The main reason a designer or analysts would use this technique is that it is a very fast. Different designs or systems can be compared against one another quickly. It does not require that the evaluator be an expert in GOMS because the procedure is an explicitly laid out recipe. A major caution is that the algorithm is designed to estimate the execution time for an expert user, which is typically faster than the time for a new user or an unfamiliar task.
See also
External links
- GOMS Analysis Techniques - Final Essay
- The CogTool project has developed an open-source tool to support KLM-GOMS analysis.
- GOMS by Lorin Hochstein
- The CogTool project at Carnegie Mellon University
- KLM-GOMS by Ethan Glasser-Camp
References
- This article incorporates text from Dr. G. Abowd: GOMS Analysis Techniques - Final Essay, which has been released into GFDL by its author (see [1]). Original references follow.
- Dix, A., Finlay, J., Abowd, G., Beale, R., Human Computer Interaction , Prentice Hall, 1993
- Lecture Notes, Abowd, G., CS6751, Georgia Institute of Technology, Nov-1997
- Kieras, D., John, B., The GOMS Family of Analysis Techniques: Tools for Design and Evaluation, CMU-HCII-94-106, 1994
- Kieras, D., John, B., Using GOMS for User Interface Design and Evaluation: Which Technique?, June-1996
- Kieras, D., John, B., The GOMS Family of User Interface Analysis Techniques: Comparison and Contrast
- Lecture Notes, CS5724, Virginia Tech, Fall 1996