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5.3. DETAILED DESIGN
By this point in the design, all the main windows have been laid out and all the primary high-level tasks and questionable interaction sequences have been prototyped. Only the final graphics, terminology, a stack of dialogues, and a myriad of small interactions remain to be designed. These can all be recorded and communicated to the development team through a Graphics and Interaction Specification that contains the full menus, a picture of each window, a description of all mouse actions on each responsive element of each window, a list of dialogues including a picture and description of each non-standard dialogue, and a set of target response times for each type of interaction.
The metaphor and platform environment are the best source of graphic ideas. The graphics should capture the essence of what they represent, the most important element, rather than being just crude images of real world objects. Mullet and Sano (1995) contain much practical advice on graphics and layout. The metaphor, platform, and real-life scenarios should be reviewed for terminology that presents a consistent view of the application.
The remaining interaction mechanisms necessary to support the remaining tasks in the task tree should be added. Take care not to clutter the design with seldom used elements. Much of what remains will likely be added as menu items and dialogues. Organize the menus according to platform guidelines. Menus are typically organized by selection and function. For example, a Text menu will contain formatting options for text selections. The same-kind-of-object guideline can be broken when the same functionality crosses many kinds of objects, e.g., Format. Task-based menus, where all the items are subtasks of some higher-level task, should be avoided as users have a great deal of difficulty locating the menu that has the desired command.
All platform guidelines describe dialogues in some detail. After a careful review to insure that each dialogue is needed, task flow, spatial grouping, consistent terminology, and platform-standardized layouts should be used to help make dialogues clear and compact.
6. SUMMARY
There is a large gap between a set of requirements and a finished user interface, too large to be crossed in one leap. This gap is most easy traversed by developing two intermediate models: essential and user. Modeling strips away the irrelevant details, freeing the designer to focus on the central issues. It is this focus on the essential that often leads to significant insights and inspiration.
The design proceeds in four steps:
Scenarios form the primary thread in this process, keeping the designer focused the users activities as the background scenarios are first extracted and then transformed across these steps. Patterns of human perception, behavior, and activity guide these transformations; metaphor is central to the essential model-to-users model transformation while an understanding of human perception, cognition, and interaction is central to the users model-to-interface design transformation. Platform-specific guidelines also aid in the selection of representations and controls used in the interface design.
Rough sketches are used throughout this process as an aid to visualizing the current stage of the design, but sketches cannot represent the dynamic nature of the interface in a compressive manner. The designer must build interactive visual prototypes to better understand the actual interactions, to test the design before it is coded and more difficult to change, and to communicate the finished design to developers and customers.
Design is not a straight-line activity that moves smoothly from step to step. It is messy, requiring the generation of many alternatives at each step and many iterations as ideas are developed and tested, returning to users time and again to check earlier decisions. This is what makes designing for people so much fun.
7. REFERENCES
Apple Computer, Inc., Apple® Human Interface Guidelines, Addison-Wesley, Menlo Park, CA, 1987.
Apple Computer, Inc., Newton User Interface Guidelines, Addison-Wesley, Menlo Park, CA, 1996.
Constantine, L. L., Essential models, Interactions, 2(2), 3446, April, 1995.
GO Corp., PenPoint User Interface Design Reference, Addison-Wesley, Menlo Park, CA, 1992.
Holtzblatt, K. and Beyer, H., Making customer-centered design work for teams, Communications of the ACM, 36(10), October, 1993.
IBM, Inc., Object-Oriented Interface Design, Carmel, Que Corp., IN, 1992.
Mullet, K. and Sano, D., Designing Visual Interfaces, Prentice Hall, Englewood Cliffs, N.J., 1995.
Nass, C., Steuer, J., and Tauber, E., Computers are social actors, Proceedings of CHI94, Boston, MA, 1994.
Papanek, V., Design for the Real World, Academy Chicago Publishers, Chicago, 1984.
Perkins, R., Keller, D., and Ludolph, F., Inventing the Lisa Interface, Interactions, 4(1), 4053, January, 1997.
Wroblewski, D.A., The construction of human-computer interfaces considered as a craft, in Taking Software Design Seriously, 119, Karat, J., Ed., Academic Press, San Diego, 1991.
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