Inference Engine and Scheduler

It might seem, if the knowledge base contains all the rules that are needed to reason about some topic and these rules are internally consistent, that conflicts could not arise, but conflicts can appear as readily within an expert system as they can in the laboratory. For example, consider the two instructions  

There is a backlog of samples for analysis. To reduce the backlog, first process those samples whose analysis can be completed in the shortest time. 

All samples sent by the hospital should be processed without delay. 

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