481: Foundations of Human Computer Interaction
Notes Section #2
Task-Centered System Design
Task-centered system design, a variation of user centered design, is a
technique that allows developers to design and evaluate interfaces based
on users' real-world tasks. As part of the design, it becomes a requirements
analysis (with the requirements being the tasks that need to be satisfied).
As part of evaluation, the evaluator can do a walk-through of the prototype,
using the tasks to generate a step by step scenario of what a user would
have to do with the system. Each step in the walkthrough asks the questions:
is it believable that a person would do this; and does the person have
the knowledge to do it? If not, then a bug has been found.
An assignment on task-centered
design and prototyping provides students with hands-on practice
in task articulation and prototype walkthrough.
Task-centered system design: [PDF]
Task-centered system design
The task-centered process
Developing task examples
Task scenarios and walkthroughs
Greenberg S. (2002) Working Through Task Centered System Design.
in Diaper, D. and Stanton, N. (Eds). The Handbook of Task Analysis for
Human-Computer Interaction. Lawerence Erlbaum Associates.
Lewis, C. and Rieman, J. (1993) Task-Centered User Interface Design:
A Practical Introduction. Entire book available as on-line
Cooper, A. (1999) The inmates are running the asylum.
Optional Readings from Baecker Grudin Buxton and Greenberg
Optional: Chapter 3: Considering Work Contexts in Design and other
readings in that section (p.187-272). This chapter focuses on the interplay
between the design of computer systems and applications, as well as the
social and organizational settings in which they are to be used. It goes
far beyond the sometimes simplistic view of task-centered system design
by considering the entire work context: from user centered, to organization-centered,
to the sociology of work, and to workplace computerization.
In-class teaching tips
I develop an example of task-centered system design by using
an imaginary client called "Cheap Shop", a catalog-based store. The situation
is that Cheap Shop's customers now browse through paper catalogs and then
place their orders by filling in a form and giving it to the clerk. Cheap
Shop is considering replacing the paper forms by a computer interface.
An initial design is proposed (provided in the exercise
mentioned above). The task examples presented in the exercise are used
to develop usage scenarios. The class then evaluates the design by a walking
a user through the example tasks step by step. Of course, many deficiencies
Major sources used to prepare lecture material
book by Lewis and Reiman describes the entire task-centered system
Cognitive and pluralistic walkthroughs are highly related techniques that
influence the way I present this material.
Bias, R.G. (1994) Chapter 3: The pluralistic usability walkthrough: Coordinated
Empathies. In J. Nielsen and R. Mack (eds) Usability Inspection Methods,
p63-76, Wiley and Sons
Wharton, C., Rieman, J., Lewis, C. and Polson, P. (1994) Chapter 5: The
cognitive walkthrough method: A practitioner's guide. In J. Nielsen and
R. Mack (eds) Usability Inspection Methods, p105-140, Wiley and
Sato, S. and Salvador, T. (1999) Playacting and focus troupes: Theatre
techniques of creating quick, intense, immersive, and engaging focus group
sessions. interactions, 6(5), September/October describes a techniques
for discovering uses of brand new products with no precursors.
The book Contextual Inquiry by Beyer and Holtzblatt (Morgan Kauffman
Press) describes a detailed methodology for articulating tasks, and is
highly recommended if you are analyzing complex situations.