From needs to requirements for computer systems: the added value of ergonomics in needs analysis.

It is widely recognised that ergonomists must contribute during needs analysis. However, few studies have investigated the specific contributions of ergonomists at this stage of the design process. In this study, this contribution is studied through the requirement document produced by the design team. For each requirement, the source (i.e. who formulated the requirement), justification (why the requirement is needed), type (functional, interaction, operational, physical, organizational), and scope (entire system or part thereof) were analysed. Results indicate that the various actors are complementary and work collectively to define the various dimensions of the system. With end-users, the ergonomist worked on the global aspects of the system: function, conditions of use and organizational dimension. Alone, he defined the global interaction of the system. The various functions derived from the global function were defined in collaboration with engineers. However, while engineers contributed to defining how these functions would work, as well as their technical conditions of use, the ergonomist focused on their purpose, and, with end-users, on their organizational aspects. Finally, results suggest that neither the ergonomist's specific knowledge in ergonomics, nor work analysis were sufficient to derive his requirements; both are mandatory.