The nature of expertise in industrial scheduling: Strategic and tactical processes, constraint and object management

This paper focuses on industrial scheduling expertise from a cognitive and ergonomic perspective. In line with the authors’ previous study of timetabling, it considers both a higher level of abstraction in the cognitive control of symbolic processing during scheduling, defined by strategic processes, and a lower level, specified by tactical processes. Within the tactical level of control, two dual problem spaces can be defined: the Constraints Space (CS) and the Objects Space (OS). The constraints adopted in this paper are considered as relations between variables that cannot be represented in the solution (a Gantt chart). Objects, on the other hand, are constraint satisfactions and can be represented in the solution. This study compared twelve novices and six experts as they scheduled and then rescheduled manufacturing orders with the use of a Gantt chart. Actions on the interface and concurrent verbal reports were collected. As was the case for the scheduling of timetables, experts used a higher level of abstraction than novices in the control of processing. This was particularly evident for generic procedures, which are found less often in timetabling. Experts were more likely than novices to use external representations (objects) as activity support, whilst novices managed more constraints in their heads. Finally, in comparison with object management, constraint management is proportionally more important in timetabling than in industrial scheduling.Relevance to industryA better understanding of the processes used by schedulers would bring about improvements in human–machine cooperation for scheduling. This stake is crucial to the enhancement of productivity and customer satisfaction. Moreover, the task of schedulers is to design a schedule, rather than to execute it. One of their roles is to contribute to the prescription of work carried out on the shop floor. Since scheduling decisions impact on workers, it is also important to understand schedulers’ problem-solving processes.

► We compare scheduling activity of novices and experts in timetabling and designing a Gantt chart.
► Scheduling activity is defined in terms of strategic and tactical processes.
► Experts use more strategic processes (procedures and goals management) than novices.
► Experts use more external representations (objects) within tactical processes.
► Novices manage more internal representations (constraints) within tactical processes.