An expert system program differs from a conventional program in the way knowledge is presented and processed. This difference exists because:
Thus, comparing an expert system to a conventional program:
Expert System = Knowledge Base + Reasoning Engine Traditional Program = Data + AlgorithmAn expert system is often referred to as a knowledge based system. Rather than using numerical methods, a knowledge based system applies 'rules of thumb' to a set of knowledge which is represented symbolically. To illustrate the subtle difference between knowledge based systems and expert systems, one could say that a system able to converse about the weather would be a knowledge based system even if it didn't embody any expertise in meteorology, but an expert system in the domain of meteorology ought to be able to provide weather forecasts. In a knowledge based system, one can say that the representation of knowledge is known as the knowledge base, whereas the part of the program that performs the reasoning is referred to as the inference engine.