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1.2. THE ROLE OF END USERS IN DESIGN

Designing a user interface without involving users is as impossible as designing one without pencil, paper, and computer. They are the main source of information about how things are currently done, the problems they face, and how those problems are dealt with. The designer must watch the users work, talk with them often, and give them the opportunity to try out early versions of the developing design. They will express needs and concerns about how the job should be done. When an end-user suggests a certain way of doing something, consider it carefully. Dig deeper to understand the problem that triggered the proposal. The suggestion may be indicative of larger issues.

As the design develops, users can provide valuable comments at all stages. They can help the designer select a preferred interface from among several alternatives and polish the rough edges as the design is refined. However, end-users should not be asked to design the interface or to participate directly in design sessions. They are intimately involved in the details of the current system and are only vaguely aware of the viewpoints of other users. They do not have the designer’s knowledge of design, human interaction, and technology. Once they have participated in creating a design, they are biased and their evaluations of subsequent designs are suspect.

2. MODELS AND TRANSFORMATIONS

People use models to explain the operation and underlying concepts of systems that are too complex to be otherwise understood. A model is an abstract representation of a portion of a system that consists of the concepts, objects, relationships, capabilities, and reactions that are important to the perspective addressed by the model. The key to modeling is to find the right abstractions that explain the desired aspects, and the careful weeding out of the irrelevant details. By reducing complexity the designer can focus on what is significant, simplifying the resulting design.

By intent a model ignores portions of a system so it cannot be used to explain those portions or to describe the system at a more detailed level. Additional models are required to address those areas. As a result, a system is often described by several related models that together illuminate all the facets of interest.

The process of design by transformation utilizes two task-based models, one extracted from background information and the second a transformation of the first. The second is then transformed into the final design. In all, the design progresses through four distinct stages:

  Background Information — The requirements, real-life scenarios, and other information gathered before beginning the design.
  Essential Model — A high-level description of the application’s fundamental functions without reference to technology or how the user will actually perform them.
  User’s Model — The concepts, objects, and tasks as seen from the user’s perspective, free of presentation and interaction elements.
  Completed U/I Design — How a person will see, think about, and interact with the application.

Several sets of guidelines and patterns of human behavior are used to guide the transformations including metaphor; patterns of human interaction with the physical world, information processing, and social interaction; and guidelines for high-level U/I design, visual and audio presentation, and platform/toolkit specific layout and widget use. Figure 4.1 summarizes the design stages, models, and transformation steps described in this chapter. The arrows indicate which elements at each stage are transformed into elements at the next stage and the information used to guide that transformation. Arrows within a stage indicate that some elements help to define other elements at that level.


Figure 4.1  Stages, models, transformations, and guidelines

Design by transformation promotes “pipeline” design, i.e., as soon as the central elements at one stage have been defined, work can begin on transforming them into next stage. Usually several alternative transformations are possible. The designer can determine the most promising alternatives by using the structure of a stage to identify and define its central elements and then try out trial transformations into the subsequent stage. When difficulties are encountered, the design focus returns to the prior stage and other alternative transformations are tried. The details of each stage are completed later as confidence in the trial design increases.


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