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© 1997 Copyright on this material is held by the authors.
The success of any interactive computer system - from either a vendor or user point of view - depends on a number of different factors, including functionality, performance, cost, reliability, maintenance, and the quality of the user interface. All these factors are of roughly equal importance, and a serious failure in any one of them can cause a failure of the system as a whole.
In the past, least attention has been paid to the human interface, as designers, developers and customers focused on maximum functionality within cost and performance constraints.
Over the past 10 years, however, there has been a growing recognition that the success of computer products in the marketplace, and as tools in business environments, depends to a significant degree on the quality of the software user interface.
Ad hoc design based on intuition and limited experience is not enough to insure the successful design of this aspect of a software application. The literature offers many principles for good interface design [1]. These principles can be helpful guidelines for designers. However, even if every designer in a software development organization was well versed in these design principles, this would not be enough to ensure good interface design. Many of the available design principles are based on experts' intuitions, rather than on hard data. Usually for any given design problem, they will come in direct conflict with each other, and there are no algorithms for making the tradeoffs. Design principles only bring the designer's attention to the issues which should be considered. There is no "cookbook" approach to applying these principles to ensure good interface design.
User interface design is a matter of compromise and tradeoff. We want powerful functionality, but a simple, clear interface. We want ease of use but also ease of learning. We strive for consistency across all aspects of the interface, but also to optimize individual operations. The interface designer finds him or herself constantly confronted with these kinds of conflicting goals. What is needed is a collection of techniques and methods for resolving such design dilemmas on a case-by-case basis.
Probably the most common way of resolving these conflicts and tradeoffs is "design by committee". Everyone on the project team gets in a room, and a rather unstructured debate ensues. Designers argue for their favorite design alternatives and counter arguments are put forth. Individual, and often trivial and inconsequential design decisions, often take hours, days or even weeks to resolve, and usually the winning proposal is determined by the sheer persistence and stamina of its advocate, rather than its overall merit.
Such meetings are, for the most part, an inexcusable waste of valuable time. The irony of this approach is that managers who scoff at the idea of prototyping and iterative design and testing as being unrealistic, too expensive and too time consuming, often engage in or condone the "design by committee" approach. However, prototyping and objective testing methods could easily be carried out in less time than is often spent in these endless design meetings.
Software designers and developers need methods and techniques to help them effectively manage the design of the user interface, and make good design decisions for a given product with its particular set of end users. The cost-effectiveness of applying such methods is well documented [2]. The purpose of this tutorial is to present and discuss such methods and techniques within the overall context of a typical modern software development life cycle. Practice - rather than theory - is the main focus of this tutorial.
The tutorial is organized around a typical modern project life cycle, and presents an overview of usability methods which can be applied at different points in the development process. These methods include:
2. Bias, Randolph G. and Mayhew, Deborah J., Eds., Cost-Justifying Usability, Academic Press, 1994
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