GOMS

GOMS (short for goals, operators, methods and selection rules to German: goals, operators, methods and selection rules ) is one way to look at the human-computer interaction. The concept was developed in 1983 by Stuart Card, Thomas P. Moran and Allen Newell and her book Human Computer Interaction published. GOMS makes it possible to cover an entire family of models of development.

Survey

GOMS segments the user interaction with a computer in elementary actions. These actions may be physical, cognitive or perceptive. By means of elementary actions user interfaces can be studied as a reference system. The different versions of GOMS also various aspects of a user interface can be investigated precisely.

In all variants, the procedure in the same system.

  • Goals are the user's goals and mostly dismantled into smaller actions.
  • Operators are the actions that the user is permitted to make, they are determined by the software.
  • Methods are chains of intermediate targets, and operators that can merge to reach the destination.
  • Selection Rules are used by the user to decide in which situation which method is in use.

The selection rules are often ignored in the typical GOMS analysis. In addition, the definition of each entity for the using the designer or analyst is often subjective. For example, one person is the operator for the other person can be a target. Furthermore, the degree of granularity is fixed on them, what is to be studied.

Variations

The simple and original GOMS, introduced by Card, Moran and Newell is now referenced as CMN - GOMS. Keystroke Level Modeling ( KLM ) is a consequent GOMS technique and has been featured in an article in 1980 in advance, and in 1983 described in detail again. This technique involves some simplified assumptions that simply make it a limited GOMS version. The third variant of GOMS is the Natural GOMS Language. This technique is very restrictive, but also very natural contemporary language to construct a GOMS model. The last GOMS variant CPM - GOMS. This technique is based on mapping the human skills and Kognitivprozesse. The advantage of CPM - GOMS is that it allows to model the parallel information processing by the user. It is also the most difficult to implement GOMS technique.

Success of GOMS

A successful implementation of CPM - GOMS was implemented in Project Ernestine the New England Telephone. It was compared to a new ergonomic working environment with the old work environment at point performance of the telephone operator. CPM - GOMS analysis had predicted a deterioration of productivity by 3%. After a four -month-long trial period and examined 78 240 phone calls an actual deterioration of 4% in the new work environment was found. Even if the new working environment less keystrokes needed as the old one, was not clear by the experiments why a deterioration in productivity occurred. However, it could show the CPM - GOMS analysis that the new working environment, the time between the calls did not use. The CPM - GOMS was not only a closer indication of the problem, it could also provide more information about the situation.

Specific studies show that predicted by GOMS processing times match quite well with real measured times.

Weaknesses of GOMS

All GOMS techniques can provide useful information, but they also have some disadvantages. None of these techniques take into account the unpredictability of the user, like dealing with fatigue, by the social environment or organizational factors. The techniques are very specific in the basic move operators, but less accurate in the basic cognitive actions. It is a fact that some slip-ups in the development of systems can not be avoided, but none of the GOMS allows the modeling of errors ( some special error situations are extensions of GOMS but can be represented, for example, there is a modeling, in with keyboard navigation web pages, the probability of an accidental loss of focus by user error taken into account). In addition, the models work under the assumption that a user knows at any moment what he has to do. This is applicable only to professional users, novice users are not considered.

However, some newer special GOMS models allow to describe the interaction of disabled users.

The functionality of a system is not considered, only the usability. Would the functionality into account, recommendations could be ordered by an evaluation which actions should be executed by the system ( for example, a mouse click). The personality or habits of the user are also taken into account by any model. All users are considered equal exactly. KLM except presuppose all the techniques that the evaluator has a deep understanding of the theoretical foundations of GOMS models, such as Cognitive Complexity Theory or human-computer interaction. This limits the effective use of GOMS for large companies that can afford appropriate experts.

Software

Some tools for generating and evaluating GOMS models:

  • GOMSED
  • QGoms (Quick Goms)
  • CogTool, KLM -based modeling tool
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