User/Human-Centered Design Principles

Human-centered design is applicable to any product or system development.  The magnitude of the effort required depends upon the complexity and criticality of the product or system.  Time, personnel, and materials will be less for a public-service Automated Teller Machine than for a safety-critical Air Traffic Management system.  However, the human-centered design principles applied to each are the same:

• Multi-disciplinary design

• Function analysis & allocation to "human-side" or "machine-side"
• Design solution iteration
• Active user involvement.

Multi-disciplinary design.  User/human-centered design requires a multi-disciplinary design team, typically representing:  users, operational managers, domain specialists, systems engineers, hardware and software engineers, visualization designers, training personnel, etc.  Users are system operators, maintainers, supervisors, managers, and other personnel interfacing with or impacted by the system.  Human Factors specialists take the lead in the design activities associated with human role definition, function allocation, job design, task/procedure development, and human-to-system interfaces.

Function analysis & allocation.  Early in system development, decisions are made on the degree of automation to be employed.  These decisions should be based on the envisioned role of the human in operation and maintenance.  Based upon the capabilities and limitations of each, functions are allocated to the "human-side" or the "machine-side" of the system.  Careful human-centered function allocation ensures the system will support user capabilities and augment human limitations.  As design proceeds, functions are decomposed into tasks and tasks into procedures, emphasizing usability throughout the process.

Design solution iteration.  Solution iteration provides the means by which evaluations and assessments are performed and feedback incorporated consistently throughout system development.  This orderly, planned progression of activities encompasses early concept formation through prototyping, build, and test.

Active user involvement.  The user actively participates throughout system design and development, providing valuable knowledge of task context, task content, and existing system shortfalls.  Importantly, users provide feedback needed for interface design refinement, modification, and iteration.

These principles are applied through six human-centered design steps explained in the next section.