Cultivar disease susceptibility ratings were determined from published information and through personal communication with growers, orchard consultants and university personnel. Incidence of scab this season and last season are supplied by the grower within the orchard profile. The potential for infection since the last fungicide application is determined by a subroutine. Once the factors which describe the goals of the apple scab module are determined, the relationship of these factors to each other is decribed. The specific relationship of the factors which describe a goal is displayed in a dependency network.
Dependency networks are types of decision trees that utilize Boolean logical approaches.
Dependency networks are valuable because they provide a 'hardcopy' reservoir of system logic and are the means of communication among domain experts and programmers. The dependency networks are the primary mechanism of communication between the subject matter experts and the programmers. These 'logic pictures' also provide a hard copy record of the system's operating logic. This record is most useful in the logic updating process done by the expert as new knowledge is acquired. The pest management modules alone represent 135 dependency networks.