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Producing effective activity graphs and scenarios has proved to be very important to the success of the usability work. They are very good ways to capture and visualize the tasks that the system is to support and an excellent platform for modeling a suitable user interface.
The central usability activities presented in this chapter are the two workshops to produce the conceptual model and the user interface design. Concentrating the work to a limited time and space (a few days in a design room) provides a number of benefits:
The case study has provided us with valuable experience that has led to improvements of the Delta Method. Some of them have already been used in subsequent projects and have resulted in improvements of both the process and the result. An example of this is the work process of the workshops that has improved considerably in subsequent projects. Discussing possible metaphors during time-outs was introduced as a way to cool down heated design discussions, but it also proved to be an effective way to interleave high- and low-level design activities. During the walk-through of the background information, we now also identify one or two core activities for each activity graph. These activities are the first ones to be transformed into focus areas. This helps us address the most important, and often most difficult, parts first and forces the remainder of the design to conform. In later projects we have also added time (20 to 30 minutes) for the team members to work individually on transforming the activities into focus areas. The parallel designs are then presented on a white-board and merged into one solution, retaining the best ideas from all designs.
The most tangible result from the conceptual design phase is a structure of system services described with UEDs. Since it is based on the activity graphs, it generally reflects the order in which work tasks are carried out. However, the focus areas also include the user objects. This creates a more object-oriented user interface with greater freedom of choice of the order in which to perform tasks. So far the user interfaces have been object oriented rather than structured, but a heavier focus on the system services would allow for a more structured interface.
The second workshop, turning the model into a user interface paper prototype, has become much more structured as a result of the case study, and we have moved our posting of intermediate results from the hallway into a design room. The level of detail in the paper prototype has varied considerably across projects and also between different parts of the same prototype. We are still working to find the proper balance.
One of the most important conclusions from the study is that a method such as Delta does not stifle the creativity that is needed to design good user interfaces. Instead it helps to structure the work so that the combined force and creativity of a usability team can be used efficiently during the design of the user interface.
8. ACKNOWLEDGMENTS
I would like to acknowledge the members of the unofficial Delta Group at Ericsson Radio Systems in Linköping, with special thanks to Åsa Bäckström, Åsa Dahl, and Cecilia Bretzner. Thanks also to Jonas Löwgren of Linköping University Susan Dray of Dray & Associates and the members of ZeLab, The Systems Engineering Lab at Ericsson, who have made valuable comments on this chapter.
9. BACKGROUND TO THE DELTA METHOD
The Delta Method was developed as a joint effort by Ericsson in Linköping and Linköping University. The method development group consisted of technical communicators and system designers at Ericsson, and researchers within these fields at the Linköping University. The researchers represented the Department of Computer and Information Science and the Institute of Tema Research, Department of Technology and Social Change. The development was supported by the Swedish National Board for Industrial and Technical Development (NUTEK). The project was a part of the ITYP venture for increased efficiency and skill in the services sector.
The Delta Method is marketed and distributed outside Ericsson by WM-Data Education in Linköping, Sweden.
10. REFERENCES
Ericsson Infocom, The Delta Method Handbook., Internal Ericsson Document, 1994.
Goldkuhl, G., Verksamhetsutveckla datsystem, Intention AB, Linköping Sweden, 1993.
Gould, J. (1988). Designing usable systems, in Handbook of Human-Computer Interaction, Helander, M., Ed., Elsevier, Amsterdam, 1988, 757-789.
Holzblatt, K. and Beyer, H., Making customer-centered design work for teams, Communications of the ACM, 36(10):93-103, 1993.
Karat, J. and Bennett, J.L., Using scenarios in design meetings a case study example, in, Taking Software Design Seriously: Practical Techniques for Human-Computer Interface Design, Karat, J., Ed., Harcourt Brace Jovanovich, San Diego, 1991, 6394.
Löwgren, J., Human-Computer Interaction What Every System Developer Should Know, Studentlitteratur, Lund Sweden, 1993.
Rantzer, M., The Delta Method A Way to Introduce Usability, in Field Methods Casebook for Software Design, Wixon, D. and Ramey, J., Eds., Wiley Computer Publishing, New York 1996, 91-112.
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