CHI 97 Electronic Publications: Tutorials
Designing User Interfaces from Analyses of Users' Tasks
Peter Johnson, Stephanie Wilson and Hilary Johnson
HCI Laboratory, Department of Computer Science
Queen Mary and Westfield College
University of London
Mile End Road
London E1 4NS UK
+44 171 975 5224
pete, steph, hilaryj@dcs.qmw.ac.uk
ABSTRACT
This tutorial provides a detailed introduction to task
analysis and task-based design. The focus of task analysis is
the description of work tasks, while the focus of task-based
design is designing interactive systems from the perspective
of users' work. Techniques from psychology, ethnomethodology and
sociology are used to analyse and describe users'
current work tasks. A framework for modelling work tasks
(Task Knowledge Structures) is used to represent relevant
task information. Guidelines are provided to help the design
team envision and reason about how current tasks might be
changed and improved through the design of interactive
systems. The envisioned task descriptions provide the focus
for the design and development of interactive systems that
will support the users' work.
Keywords
Task analysis, task-based design, work analysis, model-based design,
design guidelines, envisioning design, user interface design.
© 1997 Copyright on this material is held by the authors.
INTRODUCTION
Task analysis is concerned with understanding work. Task-based
design is concerned with developing interactive
systems from the perspective of the users' work and usage
of the designs. Task analysis is an important HCI technique
that enables users to be involved in the design process and
enables designers to understand users' work. Task-based
design provides work-tasks as the "common ground"
between designers and users [6]. It allows designers to
understand users' work and users to understand designs. The
aim of this tutorial is to provide HCI professionals with
applicable knowledge of how to carry out task analyses,
how to envision potential changes to users' work tasks and
how to design interactive systems from the perspective of
these tasks.
Task analysis can be used at multiple points in the design
process, to identify and scope the situation of concern, to
provide a well-grounded and detailed description of the
current work situation, to identify scenarios of usage, to
envision new ways of working and to provide benchmark
tasks against which designs can be evaluated. Moreover,
task analysis can be carried out at various levels of detail,
ranging from gaining an overview of the range and type of
tasks in a given organisation to providing a detailed
description of how a complex activity is carried out. Recent
work, reported in [3], has shown that conducting a task
analysis even after a design has been implemented is more
effective in generating redesign requirements than discount
usability approaches to evaluation. Task-based design
allows the designer to focus the design of new interactive
systems around users' current work tasks, as identified by
task analysis, and around envisionments of how users' work
might be in the future.
MOTIVATION
This tutorial is intended for HCI professionals including
designers and developers of user interfaces, human factors
practitioners and researchers. The overall objective of the
tutorial is to teach the benefits and use of task analysis and
task-based design techniques. The motivation for the
tutorial stems from a number of recent studies of design
practice which indicate that there is poor take-up of task
analysis and other HCI techniques, for reasons such as
perceived cost and actual lack of expertise.
With respect to cost, it can be more cost-effective to
introduce HCI techniques such as task analysis and
prototyping into the design process (see for example, [7]).
Moreover, [8] identified that designers consider obtaining
information about users and tasks as a major contributor to
the generation of design ideas. In surveying design practice,
[1] found that designers believed that task analysis could
contribute significantly to interactive system design and the
resulting usability of the designed systems. Knowledge
about how users perform tasks enables designers to reason
about what aspects of work could or could not be supported,
how they could be supported and what changes to the work
will come about as a result of a new design. By envisioning
how work tasks may be changed, designers and users will
be able to consider and reason about the design of
interactive systems from a user-work perspective, and to
assess the quality of the design in terms of its likely effects
upon the quality and performance of the users' work.
TUTORIAL OBJECTIVES
The tutorial has three main objectives:
- To introduce the ideas of task analysis and task-based
user interface design and to consider some of the
advantages and limitations of such approaches.
- To describe a selection of methods for analysing and
modelling current tasks, envisioning new and changed
tasks and developing user interface designs to support
tasks.
- To provide practical experience in carrying out task
analysis, task modelling and task-based user interface
design.
TUTORIAL CONTENT
The tutorial lasts one full day and involves interactive
presentations, demonstrations and small-group exercises.
The interactive presentations introduce the concepts and
techniques of task-based user interface design. The
demonstrations include a video of a task-based design case
study. The group work focuses on taking the participants
through an analysis of an activity as it is currently
performed, envisioning how it might be changed to
improve the situation and producing a design for a user
interface to a system to support those tasks in an improved
situation. This involves participants constructing various
task and interaction models and using design guidelines to
develop a user interface. One design problem is used as a
running example throughout the tutorial: designing a
system to support the querying of airline flight information
and booking a flight.
A significant portion of the tutorial is devoted to
understanding the TKS approach to task analysis and task
modelling [2] and [4], and the approach to task-based design
developed by the Adept project [5], [9] and [10].
Participants will be provided with hands-on experience of
analysing and modelling work tasks, envisioning new and
changed forms of tasks and using this as the basis for
designing a user interface. The tutorial is structured into
four major sections described below.
Part 1: Introduction
The tutorial starts by providing participants with an
overview of task-based design. The aims and motivations of
task-based design and some of its advantages and limitations
in relation to other design approaches are considered. A
demonstration is given of a complete task-based design
process, from the analysis of tasks in radiography to the
design of a user interface to an X-ray machine.
Part 2: Analysing and modelling work tasks
This part of the tutorial teaches participants the concepts of
task modelling and the methods of task analysis. It
introduces the Task Knowledge Structures framework for
modelling and analysing tasks. Practical experience is given
in selecting and using one or more methods to analyse the
task of querying and booking flights.
Part 3: Envisioning work and uses
In the third part of the tutorial, participants are taught how
to envision and reason about changes to tasks, and are
provided with guidelines to follow when considering which
aspects of tasks to change. Group exercises again offer
participants the opportunity to practice these techniques.
Part 4: Designing the user interface
The final part of the tutorial provides participants with
techniques and guidelines for developing a user interface
design from an envisioned task model, and gives them
practical experience in applying these to develop a
prototype design for a user interface to the flight booking
system. The tutorial closes with a plenary discussion and
feedback session.
REFERENCES
1. Johnson, H. and Johnson, P. Integrating task analysis
into system design: Surveying designers' needs.
Ergonomics, 32, 11, 1989, 1451-1467.
2. Johnson, H. and Johnson, P. Task knowledge
structures: Psychological basis and integration into
system design. Acta Psychologica, 78, 1991, 3-26.
3. Johnson, H. Generating user requirements from task
analyses and evaluations. 1st International Conference
on Cognitive Ergonomics and Engineering
Psychology, UK, October 1996.
4. Johnson, P. and Johnson, H. Knowledge analysis of
tasks: task analysis and specification for human-computer systems. In
A. Downton (ed), Engineering
the Human Computer Interface, McGraw-Hill, 1991.
5.Johnson, P. Johnson, H. and Wilson S. Rapid
prototyping of user interfaces driven by task models. In
J. Carroll (ed) Scenario-Based Design, John Wiley Inc.,
1995.
6. Johnson, P.
Models that shape design. Human Factors
in Computing Systems, Proceedings CHI 96, ACM
Press, 1996.
7.Mantei, M.M. and Teorey, T.J. Cost/benefit analysis
for incorporating human factors in the software
lifecycle. Commun. of the ACM, 31, 1988, 428-443.
8. Rosson, M.B., Maass, S. and Kellogg, W.A. The
designer as user: Building requirements for design tools
from design practice. Commun. of the ACM, 31,
1988, 1288-1298.
9. Wilson, S., Johnson, P., Kelly, C., Cunningham, J.
and Markopoulos, P. Beyond hacking: a model-based
approach to user interface design. People and
Computers VIII, Proceedings of HCI'93 Conference,
Cambridge University Press, 1993, 215-231.
10. Wilson, S. and Johnson, P. Bridging the generation
gap: From work tasks to user interface designs. In J.
Vanderdonckt (ed.) Computer-Aided Design of User
Interfaces, Proceedings of CADUI'96, Presses
Universitaires de Namur, 1996, 77-94.
CHI 97 Electronic Publications: Tutorials
