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