We described expert systems in chapter 11, information management, in relation to it’s used by management and non-management personnel to solve specific problems such as how to reduce production costs or improve workers, productivity. In this section we describe expert systems in more detail. As you may recall from chapter 11, an expert system is set of computer programs that performs a task at the level of a human expert. To expand on that definition an expert system is an interactive computer program that can apply rules to input in such a way as to generate conclusion. The program helps users solve problems that would otherwise require the assistance of a human expert. It is important to emphasize that expert systems are designed to be users assistants not replacements.
An expert system solves problems that require substantial expertise to understand. The systems performances depend on the body of facts (knowledge) and the heuristics (rules of thumb) that are fed into the computer. Knowledge engineers gather, largely through interviews, the expert knowledge and the heuristics from human experts in the field for which the computer based system is being designed to support decisions fields such as medicine engineering or geology. For example in the field of medicine one question that might be asked of an expert system is whether during the interviews are codified and entered into a knowledge base that can be used by a computer. An expert system has the capacity to store the collection of knowledge and manipulate it in response to user inquiries cases it can even explain its responses to the user.
# Knowledge base: a knowledge base is an expert systems database of knowledge about a particular subject. This includes relevant facts information beliefs assumptions and procedures for solving problems. The basic unit of knowledge is expressed as an IF-THEN-ELSE rule (“If this happens, THEN do this, ELSE do that”). Program can have as many as 10000 rules a system called expert TAX, for example which helps accountants figure out a clients tax options consists of over 2000 rules.
# Inference engine: The inference engine is the software that controls the search of the expert systems knowledge base and produces conclusions it takes the problem posed by the user of the system and fits it into the rules in the knowledge base. It then derives a conclusion from the facts and rules contained in the knowledge base.
Reasoning may be by a forward chain or backward chain. In the forward chain of reasoning, the user. It then proceeds to apply any rule that fits the problem. In the backward chain of reasoning the system works backward from a question to produce an answer.
# User interface: The user interface is what appears on the display screen for the user to interact with. It gives the user the ability to ask questions and get answers. It also explains the reasoning behind the answer