Bonnie E. John

The GOMS family of user interface analysis techniques: comparison and contrast

Sine the publication of The Psychology of Human-Computer Interaction, the GOMS model has been one of the most widely known theoretical concepts in HCI. This concept has produced severval GOMS analysis techniques that differ in appearance and form, underlying architectural assumptions, and predictive power. This article compares and contrasts four popular variantsof the GOMS family (the Keystroke-Level Model, the original GOMS formulation, NGOMSL, and CPM-GOMS) by applying them to a single task example.

Using GOMS for user interface design and evaluation: which technique?

Since the seminal book, The Psychology of Human-Computer Interaction, the GOMS model has been one of the few widely known theoretical concepts in human-computer interaction. This concept has spawned much research to verify and extend the original work and has been used in real-world design and evaluation situations. This article synthesizes the previous work on GOMS to provide an integrated view of GOMS models and how they can be used in design. We briefly describe the major variants of GOMS that have matured sufficiently to be used in actual design. We then provide guidance to practitioners about which GOMS variant to use for different design situations. Finally, we present examples of the application of GOMS to practical design problems and then summarize the lessons learned.

Project ernestine: validating a GOMS analysis for predicting and explaining real-world task performance

Project Ernestine served a pragmatic as well as a scientific goal: to compare the worktimes of telephone company toll and assistance operators on two different workstations and to validate a GOMS analysis for predicting and explaining real-world performance. Contrary to expectations, GOMS predicted and the data confirmed that performance with the proposed workstation was slower than with the current one. Pragmatically, this increase in performance time translates into a cost of almost

Predictive human performance modeling made easy

2 million a year to NYNEX. Scientifically, the GOMS models predicted performance with exceptional accuracy. The empirical data provided us with three interesting results: proof that the new workstation was slower than the old one, evidence that this difference was not constant but varied with call category, and (in a trial that spanned 4 months and collected data on 72,450 phone calls) proof that performance on the new workstation stabilized after the first month. The GOMS models predicted the first two results and explained all three. In this article, we discuss the process and results of model building as well as the design and outcome of the field trial. We assess the accuracy of GOMS predictions and use the mechanisms of the models to explain the empirical results. Last, we demonstrate how the GOMS models can be used to guide the design of a new workstation and evaluate design decisions before they are implemented.

The tangled Web we wove: a taskonomy of WWW use

Although engineering models of user behavior have enjoyed a rich history in HCI, they have yet to have a widespread impact due to the complexities of the modeling process. In this paper we describe a development system in which designers generate predictive cognitive models of user behavior simply by demonstrating tasks on HTML mock-ups of new interfaces. Keystroke-Level Models are produced automatically using new rules for placing mental operators, then implemented in the ACT-R cognitive architecture. They interact with the mock-up through integrated perceptual and motor modules, generating behavior that is automatically quantified and easily examined. Using a query-entry user interface as an example [19], we demonstrate that this new system enables more rapid development of predictive models, with more accurate results, than previously published models of these tasks.

Linking usability to software architecture patterns through general scenarios

A prerequisite to the effective design of user interfaces is anunderstanding of the tasks for which that interface will actuallybe used. Surprisingly little task analysis has appeared for one ofthe most discussed and fastest-growing computer applications,browsing the World-Wide Web (WWW). Based on naturally-collectedverbal protocol data, we present a taxonomy of tasks undertaken onthe WWW. The data reveal that several previous claims aboutbrowsing behavior are questionable, and suggests that thatwidget-centered approaches to interface design and evaluation maybe incomplete with respect to good user interfaces for the Web.

Tracking the effectiveness of usability evaluation methods

Usability is an important quality attribute to be considered during software architecture design. Up to this point, usability has been served only by separating a systems user interface from its functionality to support iterative design. However, this has the effect of pushing revisions to achieve usability toward the end of the software development life cycle. Many usability benefits link directly to a variety of architectural tactics in addition to separation of the user interface and these benefits can be discovered early in the life cycle. For each of 27 scenarios, we identified potential usability benefits a user could realize and an architectural pattern that supports achievement of those benefits. We organized the scenarios into an emergent hierarchy of potential benefits to the user and into an emergent hierarchy of architectural tactics used in the supporting patterns. The range of architectural tactics identified in this hierarchy demonstrates that separation is far from the only architectural tactic necessary to support usability. We present techniques that permit important usability issues to be addressed proactively at architecture design time instead of retroactively after user testing.

Extensions of GOMS analyses to expert performance requiring perception of dynamic visual and auditory information

Abstract We present a case study that tracks usability problems predicted with six usability evaluation methods (claims analysis, cognitive walkthrough, GOMS, heuristic evaluation, user action notation, and simply reading the specification) through a development process. We assess the methods predictive power by comparing the predictions to the results of user tests. We assess the methods persuasive power by seeing how many problems led to changes in the implemented code. We assess design-change effectiveness by user testing the resulting new versions of the system. We concludethatpredictivemethodsarenot as effective as the HCI field would like and discuss directions for future research.

The precis of Project Ernestine or an overview of a validation of GOMS

GOMS models of telephone toll and assistance operators (TAOS) are being constructed in an effort to provide theoretical predictions of expert performance on several dedicated workstations. This applied effort has pushed the development of GOMS modeling techniques into the area of speech input and output, and into a task where information is not always available when it is required by the TAO. This paper describes the task, heuristics for constructing the GOMS models, and parameters for making quantitative predictions of performance time.

Assessing dynamics in computer-based instruction

INTRODUCTION Project Ernestine served a pragmatic as well as a scientific goal: to compare the worktimes of telephone company toll and assistance operators on two different workstations, and to test the validity of GOMSl models for predicting and explaining real-world performance. Contrary to expectations, GOMS predicted and the data confirmed, that performance with the proposed workstation was slower than with the current one, Pragmaticly, this increase in performance time translates into a cost of