Mining Publication: Operationalizing Normal Accident Theory for Safety-Related Computer Systems

Computer-related accidents have caused injuries and fatalities in mining, as well as other industries. Normal accident theory (NAT) explains that some accidents are inevitable because of system complexity. NAT is a classic argument in organizational sociology, although it has been criticized as having imprecise definitions and lacking criteria for quantifying complexity. These limitations are addressed by a unique approach that recasts this organizational theory into an engineering-based methodology to quantify NAT complexities of computer-based systems. In this approach, complexity is categorized as external or internal. External complexity is defined by the external behavior of a system and is quantified by the following dependent variables: system predictability, observability, and usability. Dependent variable data contain the perceptions of 32 subjects running simulations of a system. The system's internal complexity is characterized by modeling system-level requirements with the software cost reduction (SCR) formal method. Model attributes are quantified using 15 graph-theoretical metrics--the independent variables. Five of 15 metrics are correlated with the dependent variables, as evidenced by structure correlations exceeding 0.25, with standard errors <0.10 and="" a="" 95%="" confidence="" interval.="" the="" results="" also="" show="" that="" the="" system="" predictability,="" observability,="" and="" usability="" decreased="" as="" nat="" complexities="" increased.="" this="" research="" takes="" a="" step="" forward="" in="" operationalizing="" nat="" for="" computerized="" systems.="" the="" research="" benefits="" mining,="" as="" well="" as="" other="">