The Human Factors Engineering approach to human-machine system design is based largely on normative design methods. This article suggests that the scope of Human Factors Engineering shall be extended to the descriptive study of system design in actual practice by the application of theoretical frameworks that emphasize the role of the system-design practitioner and organization in the design process. A comparative study of system design in normative and actual practice was conducted in the design of cognitive task allocation in a Flexible Manufacturing System (FMS) cell. The study showed that the designers' allocation decisions were influenced strongly by factors related to their own design practices, yet exogenous to the tasks to be allocated. Theoretical frameworks from Design Research were applied to illustrate differences between normative and actual practice of system design. © 2004 Wiley Periodicals, Inc.
SYSTEM DESIGN AS AN AREA OF INQUIRY
Scope and Purpose of the StudyHuman Factors Engineering studies system design mostly as a normative process, namely the application of behavioral principles to the formulation and application of systematic design rules or guidelines (Meister, 1989) prescribing what the system designer should do. This article examines the study and practice of system design through an experimental study of cognitive task allocation. According to the approach taken, the study of system design as a normative process is extended here to include a study of system design in actual practice, a descriptive study of what the system designer actually does.Historically, Human Factors Engineering has focused on system operation and the role of the human operator as a system component (Meister, 1989). The study of system design in actual practice instead focuses on system design and the role of the systemdesign practitioner (and, in extension, the system-design/engineering organization). The purpose of the study of system design in actual practice is to develop a theory that encompasses the cognitive, professional, ontological, organizational, and social dimensions of system design in actual practice. Proper understanding of system design in actual practice is prerequisite to proactively supporting system designers through decision support, cooperative design, or other means, including normative design methods. System designers