The choice of the unit of analysis for modelling real work settings

Air traffic control (ATC) is currently undergoing rapid changes as new technology is being introduced. The introduction of new technology produces adaptations of how the system performs its computation with consequences and changes in the activity for both the individual and the system as a whole. Even if ATC is a highly structured and well-documented domain, the analysis of changes and evolution in the work environment, in view of the design of new technologies, requires the definition of an appropriate-level analysis. This paper discusses two important issues related to the analysis of complex domains like ATC: the distinction between the normative task description and the actual human activity; and the choice of the unit of analysis for modelling real work settings. The paper presents a case study describing the application of distributed cognition and discusses findings and implications of this theoretical approach for the design of new technologies for ATC.