Saul Greenberg > courses > lecture topics in HCI > task-centered system design

Task-Centered System Design

Task-centered system design is a technique that helps developers design and evaluate interfaces based on users' real-world tasks. As part of design, it becomes a user-centered 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.

Overheads

• Task-centered system design: [PDF] or [Powerpoint]
• Animated prototype of a new CheapShop Interface [Powerpoint]

Handouts and resources

• Exercise: The CheapShop Interface
• Template for task centered walkthroughs

Topics covered

• The task-centered system design process
• Developing task examples
• Task scenarios and walkthroughs
• Case study: CheapShop

Readings 

1. Working through Task-Centered System Design. Greenberg, S. (2003) in Diaper, D. and Stanton, N. (Eds) The Handbook of Task Analysis for Human-Computer Interaction. Lawrence Erlbaum Associates.
   • This chapter provides an introduction and worked example of the task-centered design process. It is directly based on the materials taught in this class.
2. Chapter 9: Designing for Pleasure. In The Inmates are Running the Asylum. Cooper, A. (1999) Sams (Macmillan).
   • This chapter describes goal-centered system design, a related methodology. It discusses how one can use Personas to influence design.

In-class activities

To make this material come alive, the class will apply task-centered system design to "Cheap Shop", a catalogue-based store. In this case study, the situation is that Cheap Shop's customers now browse through paper catalogues and then place their orders by filling in a form and giving it to the clerk. Cheap Shop is replacing the paper forms by a computer interface. A previously created design has already been proposed (provided in the exercise mentioned above). Several task examples were created after the fact, and these are used by the class to evaluate this design.  The class  walks each user identified in the examples through the task step by step. Of course, the class will discover many deficiencies. Afterards, an alternative design for Cheap Shop (detailed in the prototyping module) is developed. Reading 1 details this exercise as a case study.

Additional readings

1. Task-Centered User Interface Design:  A Practical Introduction. Lewis, C. and Rieman, J. (1993). Available as Shareware. These chapters are especially relevant:
   • Chapter 1: Getting to Know Users and their Tasks
   • Chapter 4: Evaluating the Design Without Users
2. Usability Inspection Methods, J. Nielsen and R. Mack (eds) (1994), Wiley and Sons.
   • Cognitive and pluralistic walkthroughs are highly related techniques that influence the way I present this material. This book has several chapters on these methods:
   • Chapter 3: The pluralistic usability walkthrough: Coordinated Empathies. Bias, R.G.
   • Chapter 5: The cognitive walkthrough method: A practitioner's guide. Wharton, C., Rieman, J., Lewis, C. and Polson, P.
3. The Inmates are Running the Asylum.  Cooper, A. (1999) Sams (Macmillan).
   • An applied and fun book appropriate to lay interface developers. Chapter 9 was mentioned above, but Chapter 11 also relates to this topic.
4. Contextual Design: Defining Customer-Centered Systems. H. Beyer and K Holtzblatt, Morgan Kaufmann Publishers
   • describes a detailed methodology for articulating tasks, and is highly recommended if you are analyzing complex situations.
5. Chapter 3: Considering Work Contexts in Design. p.187-272. In Baecker, R., Grudin, J., Buxton, W., and Greenberg, S., eds (1995). Readings in Human Computer Interaction: Towards the Year 2000. Morgan-Kaufmann.
• 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.
6. Playacting and focus troupes: Theatre techniques of creating quick, intense, immersive, and engaging focus group sessions. Sato, S. and Salvador, T. (1999) interactions, 6(5), September/October.
   • describes a techniques for discovering uses of brand new products with no precursors.

Last updated Summer 2004