The process of interactive forward chaining inference in the medical knowledge-based system as figure 9. The system first obtains chief complaint from the patient and places it in the blackboard. The infer- ence engine then scans the rules in some predefined sequence looking for one whose premises match the contents in the blackboard or query the patient. If it finds a rule, it adds the rule’s conclusion to the blackboard, firing the rule, then cycles and checks the rules again looking for new matches. On new cycle, rule that previously fired are ignored. This process continues until no matches are found. At this point the blackboard contains facts supplied by the patient and inferred by the system.