PDF of this tutorialThree simple design principles that underlie the development of products and services (know your users, involve users early and continuously, and rapid and frequent iteration towards measurable usability targets) will be outlined in this and the following two modules. The next module discusses the usability engineering lifecycle and shows how these three design principles are kept in focus by specific activities during development.
The best way to meet users' needs—including usability—is to understand the users intimately. A user-centered approach assumes that although people vary widely, they all have particular needs that must be met. For example, where a business process is being automated, instead of automating whatever can be automated and leaving the remaining tasks to the users, a user-centered approach will assign specific tasks to the users and the system, taking into account the users' needs.
Users can often be a source of product improvement and innovation—especially lead users and early adopters. The most difficult and demanding customers often become the best partners for product improvement. Users will often use products in ways that were never intended or expected—these uses and abuses, and the problems users have as a result, are often sources of inspiration for improvement or differentiation.
Users are experts in their requirements—they understand their goals and their tasks, and they know the objects and artifacts they produce and use, the work-arounds they invent (not just the official, formal procedures), and the problems they have. However, users are not always good at describing, explaining, or predicting their behavior. Because users do not often make good designers, they must be involved in effective ways.
In particular, users develop their own conceptual model of their work. This conceptual model is never the same as the designer's model. Users always behave in surprising ways, which is why they must be involved in the design process. A successful HMI maps the users' conceptual model directly onto the software or hardware so that users may not even be aware of the HMI components.
Who Are the Users?
The first issue to be resolved is how to choose which users will be involved in the design. For consumer products, the answer will lie in the demographics of the target user population. For business productivity applications, target users are often easier to define but sometimes more difficult to access or to involve in the design process.
For almost all products, there will not be a single user or user role. Although the end user may be the primary person affected by a design, there will also be secondary users—people who have requirements that must be taken into account in the design and who are affected by the design even if they do not actually press the keys. The task of identifying the users and their different requirements is known as "stakeholder analysis."
For example, in a call center for customer assistance and queries, the call-center operators are the primary users, but the call-center managers and the customers who call are other stakeholders. Similarly, the people who decide to buy a videoconferencing service for a major corporation are often not the people who have to use it, but both of these stakeholders—the users and the choosers—have important needs that must be met.
During the early gathering of information, designers will start to understand the users' range of concerns, goals, and priorities. It is often helpful to develop a series of stereotypes—imaginary individuals whose life details and images are representative of the main user population. Developers and users alike can often relate to these portraits more easily than to dry statistics. These imaginary individuals can also star in the storyboards and scenarios that are used to gather users' requirements and explore solutions, as will be described later.
