More Than Screen Deep Toward Every-Citizen Interfaces to the Nation's Information Infrastructure (1997) / Chapter Skim
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Background Paper
Background Paper
Pages 221-242
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From page 221... ...
Rather than being fuzzy and vague as it is sometimes perceived, usability is tangible and can be quantified. Usability can be broadly defined as "ease of use," including such measurable attributes as learnability, speed of user task performance, user error rates, and subjective user satisfaction (Shneiderman, 1992; Hix and Hartson, 1993a)
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While state-of-the-art user interaction development processes are based on formative usability evaluation in an iterative cycle, much of the state of the practice is fundamentally flawed in that remarkably little formal usability evaluation is performed on most interactive systems. This is generally changing now in many industrial settings.
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The view of the user interaction component is the user's perspective of user interaction: how it works; how tasks are performed using it; and its look and feel and behavior in response to what a user sees, hears, and does while interacting with the computer. In contrast, the user interface software component is the programming code by which the interaction component is implemented.
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There are various task analysis methods to address various purposes. In HCI the primary uses are to drive design and to build predictive models of user task performance.
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Nonetheless, these models have not achieved widespread application within the tight constraints of industrial schedules and budgets because of the labor intensiveness of producing and maintaining these relatively formal and structured task representations, the need for specialized skills, and the difficulty in competing with the effectiveness of usability evaluation using a prototype. Furthermore, these techniques generally do not take into account individual differences in user classes and are often limited to expert, error-free behaviors (not representative of "every citizen" as a user)
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A very similar term, interaction style, has evolved to denote the behavior of a user and an interaction object (e.g., a push button or pulldown menu) within the context of task performance.
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This kind of opportunistic interaction is also called display-based interaction (Payne, 1991~. DEVELOPMENT METHODS AND SOFTWARE ENGINEERING The difference between user interaction and user interface software, mentioned in the Introduction, results in a need for separate and fundamentally different development processes for the two components of a user interface.
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Although software can be correctness driven, user interaction design because of infinite design possibilities and unpredictable, dynamic, and psychological aspects of the human user must be self-correcting. Thus, interaction development is an essentially iterative process of design and evaluation, one that must, in the end, be integrated with other system and software life cycles.
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A user interaction design is represented as a quasi-hierarchical structure of asynchronous tasks. User actions, interface feedback, and internal state information are represented at various levels of abstraction in the UAN.
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operationally defined and measurable goals used as criteria for success in interaction design. Even more valuable than these quantitative data are the qualitative data gathered in usability evaluations.
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Development Tools Almost any software package that provides support for the interface development process can be called an interface development tool, a generic term referring to anything from a complete interface development environment to a single library routine (Myers, 1989, 1993~. New software tools for user interface development are appearing with increasing frequency.
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These first three categories of development tools primarily address user interface software. A fourth category, interaction development tools, provides interactive support for user interaction development.
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As an example, it is unlikely that usability methods developed for desktop applications will apply directly to virtual environments, one of the most exciting areas of applications development. Despite intense and widespread research in virtual environments, very little work has been applied toward developing the usability methods that will be required to evaluate this new technology a necessary coupling if virtual environments are to reach their full potential.
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For this large-scale environment with its diversity of user types and characteristics, its variety of application types, and potential user isolation, usability takes on special importance. Additionally, the interaction styles and techniques of future products can be expected to expand beyond the currently ubiquitous WIMP windows, icons, menus, pointers or desktop-style interface.
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There is an ongoing need for new high-impact usability evaluation methods. High impact means cost effective, applicable to a wide variety of application types (e.g., World Wide Web applications)
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More significantly, a usability database tool would afford some "memory" to the process, amortizing, through reuse of analysis, the cost of results across design iterations and across multiple products and projects. Beyond organizational boundaries, a collective usability database could serve as a commonly accessible repository of a science base for the HCI community and as a practical knowledge base for exemplar usability problems, solutions, and costs.
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Christie (Eds.) , Applying Cognitive Psychology to User-Interface Design.
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(1994~. Comparative Usability Evaluation: Critical Incidents and Critical Threads.
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(1993~. State of the Art in User Interface Software Tools.
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(1990~. User Interface Design.
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