This produces the additional statement Mary Louise is Paul's grandmother. An expert system computer program uses the principle described above. Given a knowledge base, its inference engine attempts to reason out new facts which will lead the user toward a goal. However, the concept of an expert system relies heavily on a human factor. Let's look at an example.
Cardiac arrests are common in a hospital.
However, an experienced cardiac specialist, who knows all the different heart rhythms and drugs to prescribe, may not be around. It would be nice if the closest nurse, paramedic, or less experienced doctor could use the knowledge of the cardiac specialist when he is not around. In this case the cardiac specialist is the expert . He has in-depth knowledge and is considered an authority in his field. However, experts rarely know how to program computers.