An expert system is a computer program that combines a knowledge base of information about a particular field with a system of rules that applies the knowledge to specific situations. Such a system can analyze a problem in a given discipline and provide solutions for it. The system of rules, often called an inference mechanism, consists of a complicated "tree" of logical operations that is carried out by the program. An expert system is considered a form of artificial intelligence. Edward Feigenbaum, a computer specialist, and Joshua Lederberg, a professor of genetics, are generally credited with developing the first expert system at Stanford University in the 1960s. Their program, DENDRAL, determines the structures of organic chemicals using only complex spectroscopic or instrument readings. Other researchers realized that expert systems would be useful in medical diagnosis and began developing programs to assist physicians in investigating disease. An...