expert system is sofware that attempts to provide an answer to a problem or clarify uncertaintainties were normally one or more human expert would need to be consule. Expert systems are most common in a specific problem domain, and is a traditional application or subfield of artificial intellegence. A wide variety of methods can be used to simulate the performance of the expert however common to most or all are 1) the creation of a so-called "knowledgebase" which uses some knowledge representation formalism to capture the Subject Matter Expert's (SME) knowledge and 2) a process of gathering that knowledge from the SME and codifying it according to the formalism, which is called knowledge engineering. Expert systems may or may not have learning components but a third common element is that once the system is developed it is proven by being placed in the same real world problem solving situation as the human SME, typically as an aid to human workers or a supplement to some information system.

rule-based expert system is an expert system based on a set of rules that a human expert would follow in diagnosing a problem. Conventional rule-based expert systems, use human

expert knowledge to solve real-world problems that normally would require human intelligence. Expert knowledge is often represented in the form of rules or as data within the computer.Depending upon the problem requirement, these rules and data can be recalled to solve problems. Rule-based expert systems have played an important role in modern intelligent

systems and their applications in strategic goal setting, planning, design, scheduling, fault monitoring, diagnosis and so on.