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4.5. HETEROGENEOUS USER GROUP
Consumer products such as cellular telephones have many users with different backgrounds and expectations. A diverse group of users will want to accomplish similar tasks in many different ways. The Orbitor user research indicated that the product would have to support two levels of users novice and expert. It had to provide a simple and discoverable interface to novice users, but not at the expense of a fast and powerful interface for experienced cellular phone users. The team therefore designed the Orbitor with context-sensitive help prompts for the new user. Experienced users would be able to personalize the user interface to speed up common tasks by reducing the number of prompts. Short cuts would also be available to the power user. As expressed by Collins (1995, p.66), A successful user interface will not lose its appeal as the user becomes expert, and will take advantage of any expertise the user brings to the application from prior experience.
5. MANAGING AND DOCUMENTING THE ITERATIVE DESIGN PROCESS
The term iterative design has been used to describe the design process throughout this chapter (see Figure 11.8). A concurrent iterative process for the Refinement and Analysis and Formal Design Stages is critical for any new generation projects. However, the Exploratory Design Stage discussed first is not iterative or convergent; in fact it is divergent, and the initial exploratory concepts are deliberately designed to be far removed from what users would expect to see in a current real product. The various exploratory concepts represent a breadth of ideas.
Figure 11.8 Concurrent iterative development model.
One of the key project management challenges is to keep the iterative process on track and moving toward a more usable design. For an iterative design process to work within the constraints of the product development cycle, two conditions must be met. First, the initial design must be reasonably close to the final product design. Second, successive iterations must converge on the final improved product at acceptable speed to meet project delivery deadlines.
5.1. POTENTIAL PROBLEM WITH ITERATIVE PROCESS
There are two common problems with iterative design. One is that the initial design is so far from an acceptable final design that it is impossible to evolve toward it. Another is that the initial design might immediately cut-off development in the right direction and successive iterations may show no improvement over the initial design.
Iterative design cannot replace up-front analysis. It is extremely frustrating and inefficient to do iterative design if the design team has no common understanding of the users requirements. The team must have a systematic decision-making process (see Table 11.4) and clearly defined metrics with which to evaluate each successive design iteration. Optimally, the team should record design decisions and design rationale to avoid repetition.
Level 1. Does the new design meet the list of user values and detailed product attributes? |
Level 2. Is the users conceptual model clearly communicated in the design? |
Are the metaphors appropriate to the user and to the task |
Does the flow of the dialogue in the user interface match the users task flow? |
Level 3. Does the interface follow basic principles and guidelines for the good UI design? |
Some of these guidelines as suggested by Norman (1988) and Neilsen (1993) include: |
Provide meaningful feedback to the users actions |
Provide visual clues (affordances) to the user about the function of an object |
Show an understandable relationship between a control and its function (mapping) |
Use a simple and natural style of dialogue and interaction |
Provide a consistent method of interaction for the user |
Provide a meaningful feedback for recovery from errors |
Provide shortcuts to experienced users |
Level 4. Detail Design: |
Is this the optimal layout for each screen give certain constraints? (e.g., small display size, anthropometric data regarding minimum touch target size)? |
Is this the best GUI widget or control to use to accomplish a defined task given certain constraints (e.g., usable in the mobile environment)? |
Level 5. When the design is tested with end users, does it meet usability requirements? |
Note: This is by far the most important decision-making criteria |
5.2. DECISION CRITERIA FOR TRANSLATING USER INFORMATION INTO A USER INTERFACE
Having brought together multiple design concepts and user information in the Exploratory and Refinement and Analysis Stages, the Orbitor design team then had to translate this into a working user interface. In the Formal Design Stage, a hierarchical decision-making process was used to guide the design of the user interface. This hierarchy can be expressed as a series of questions with associated decisions to be made before progressing to the next level (Table 11.4).
Asking Level 1- and Level 2-type questions was the method by which high level design decisions were made. More specific questions regarding the high-level model were addressed at Level 3. Detail design issues were addressed at Level 4 and further refined by input from usability testing of UI simulations (Level 5). A hierarchical process such as this can speed up and simplify the constant design trade-off decisions that are associated with any development project.
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