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 usability bug has been found.
An assignment on task-centered design
and prototyping provides students with hands-on practice in task articulation
and prototype walkthrough (see the lecture notes).
Overheads
Topics covered
- Task-centered system design
- The task-centered process
- Developing task examples
- Task scenarios and walkthroughs
Required Readings
- 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. Lawrence Erlbaum
Associates: [Acrobat]
- Cooper, A. (1999) The inmates are running the asylum
(Chapter 9). Sams
(Macmillan), Excerpt on Personas
Optional Readings
- Cooper, A. (1999) The inmates are running the asylum
(Chapter 10& 11). Sams
(Macmillan), Excerpt on Personas
- Baecker, Grudin, Buxton and Greenberg 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.
- The online version of
Lewis
and Rieman's book (from The Handbook of Task Analysis for Human-Computer
Interaction) which Greenberg's book chapter is based upon.
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. At first glance
the system may appear to be adequete but after completing the task-centered
evaluation many deficiencies
are discovered.
Major sources used to prepare lecture material
- The
shareware book
by Lewis and Reiman describes the entire task-centered system design process.
- 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 Sons.
- 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.