EXPERT SYSTEMS

Expert systems use a broadly related but different approach. They are computer programs which are intended to exhibit intelligence at the level of not merely an average human but of an expert in the field. To understand, let us see how a medical practitioner diagnoses what is wrong with a patient. He has his medical knowledge at the back of his mind. In a simplified sense, this can be abstracted into a set of rules: e.g. if a patient has fluctuating temperature, shivering, he has malaria, body ache and congestion indicate flu - and so on. All of us do tend to act as medical experts using similar rules. We make mistakes in our amateur diagnosis primarily because our rule base is neither accurate nor extensive. What if such rules, obtained from real experts, are incorporated into a computer program? Thanks to infallible memory, potentially unlimited number of rules, it should do even better than a human expert! It could even outperform medical specialists by the simple trick of integrating the expertise gained from several specialists. It should work particularly well in complicated cases where the patient has several diseases. A human expert might get confused due to the overlap of symptoms. Also in case of rare diseases, which the doctor may not be familiar with.

Such an expert system should have an inference engine which looks at symptoms and draws inferences using the rules given to it. In addition, it should have an interaction facility to accept the rules that humans communicate to it. Also, it should be able to tell the human user the basis of its reasoning: why, in a given situation it has come to a particular diagnosis. Many of us know that medical experts are often reticent in this respect. They may say, “This is my diagnosis, take it or leave it,” and refuse to discuss details any further.

The nice thing about expert systems is that much of what needs to go into them is common for all application areas: medical diagnosis, automobile repair or choice of machine tools for a particular job, or even playing a game of chess. Only the rules will vary from application to application. Expert systems therefore have a shell which incorporates all these interaction facilities. For any given application, you only need to insert a specialized rule base.

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