Bonnie E. John (1) and Wayne D. Gray (2)
(1)
Computer Science, Psychology &HCII
Carnegie Mellon University
Pittsburgh, PA, 15213, USA
Tel: +1-412-268-7182
E-mail: bej@cs.cmu.edu
(2)
Psychology & KrasnowInstitute
George Mason University
Fairfax, VA 22030-4444
Tel: +1-703-993-1340
E-mail: gray@mary.fordham.edu
An important concept in analyzing the total task time for
complex parallel tasks is the critical path. When
activities occur in parallel, one sequence ofactivities will
take more time than parallel sequences of activities;
the critical path is the sequence of activities that takes the
longest and determines the total time for the entire task.
The critical path is displayed in boldface in Figure 1.
Figure 1.
Critical path for task.
Attendees at this tutorial learn how to create large models
of a total taskfrom small building-blocks representing
different activities. Figure 1 shows how the large model of
a telephone operator handling a collect call (stretching
across the bottom third of the page) is constructed from
building block schedule charts representing system response
time, the perception of sounds and visual information,
conversations, hand-movements, etc.
Abstract
GOMS is a family of techniques for analyzing human
performance in terms of the Goals, Operators, Methods and
Selection rules necessary to perform atask. Traditionally,
GOMS has approximated human performance as perceptual,
cognitive, and motor activities performed sequentially.
However, many tasks require users to perform activities in
parallel, e.g., visually searching for information, while
listening to a customer, while typing. This tutorial will
teach aversion of GOMS, CPM-GOMS, that predicts
performance on such tasks andsaved an industrial
organization millions of dollars through the evaluation of
alternative system designs.
Keywords:
GOMS, user models, cognitive models,
analytic methods
CONTENTS OF THE TUTORIAL
We begin with an introduction to the general concept of
GOMS, that skilled human performance can be analyzed in
terms of the Goals, Operators, Methods and Selection rules
necessary to perform a task [1]. We examine several
versions of the GOMS concept with emphasis on the
relationship between the various techniques. We then
present CPM-GOMS, the variant of GOMS that expresses
skilled performance on tasks with parallel activities with
schedule charts [2,3]. We demonstrate how to construct
such a model, how to interpret its predictions, and how to
make what-if evaluations of design alternatives. Attendees
modify existing models and construct their own CPM-
GOMS model for a new task using project
management software on personal computers.
CPM-GOMS
In CPM-GOMS the parallelism of a task is represented in a
schedule chart (Figure 1). Each activity in a task is
represented as a box with an associated duration.
Dependencies between activities are represented as lines
connecting the boxes. For example, a telephone operator
helping a customer cannot hit the collect-call key until s/he
hears the customer request a collect call.Therefore, there
would be a dependency line drawn between a
box representing the perception of the word "collect" and
boxes representing cognitive operators that verify the word
"collect"and initiate pressing the collect-call key. The
boxes and their dependency lines are drawn according to a
detailed understanding of the task, goal decomposition,
and operator-placement heuristics (3).
(Caution: Large 536857 mbyte GIF file) .
