Production rules are one of the most popular and widely used knowledge representation languages. Early expert systems used production rules as their main knowledge representation language. For example, MYCIN, which is also considered one of the first research works in medical informatics, has production rules as its knowledge representation language.
Production rule system consists of three components, i.e., working memory, rule base and interpreter. The working memory contains the information that the system has gained about the problem thus far. The rule base contains information that applies to all the problems that the system may be asked to solve. The interpreter solves the control problem, i.e., decide which rule to execute on each selection-execute cycle.
Production rules as a knowledge representation language has the following advantages: