What is a rule-based system?

A rule-based system is a useful knowledge-based system that allows rule-based reasoning. Such Rule-based systems consist of a database of facts (fact base), a set of rules (rule base) and a control system.which is equipped with a rule interpreter (inference engine or business rule engine).

The rules are constructed according to the if-then-else principle. The IF part is called the premise and the THEN part is the conclusion. The control system is to make an identification of appropriate rules and apply selected rules and update the database. The selection mechanisms are data-driven or goal-driven.

Rule-based systems form the basis of expert systems. Rules are managed in a business rule repository, which is part of a business rule management system.

What are the applications for rule-based systems?

It comes to the increasing Use of rule-based systems in production planning and production control. These systems are used in particular in industries with a wide variety of consumer and investment goods. They are used in the furniture industry, in mechanical engineering, in the automotive industry and in the electrical industry.

Product configurators know what dependencies there are and inform about them. For example, there are certain combinations of features. A customer can order a convertible, but it cannot have a "sunroof". When ordering a fully automatic "air conditioning system", the vehicle also needs a stronger "battery" at the same time.

Rule-based systems are also used for the distribution of worldwide vehicle orders. For example, there are rules for vehicle and aggregate plants of car manufacturers. The rulebook of a car manufacturer has thousands of product and production rules.

How are rule-based systems structured?

Rule-based systems are the most common type of knowledge-based systems (expert systems). The components are a rule base (set of rules) and an inference mechanism (inference engine). The inference mechanism determines which of the rules to apply and there are several possible strategies that can be used. For example, there is either forward chaining or backward chaining of corresponding rules.

What are the rules in a rule-based system?

The rules are simply formalised conditional sentences. They have the form:

If (if) A, then (then) B

This is where the meaning comes from:

If A is true (fulfilled, proved),
then conclude that B is also true.

A and B are statements. The "if"-part formula of a rule is called the premise or antecedent of the rule. The "then" part formula is called the conclusion or consequence. As soon as the premise of a rule is fulfilled, the rule is applied.

If this rule always applies, it is called a deterministic rule. If the consequence of a rule is connected with a corresponding action, then we have a production rule. These rules are often used in corresponding production systems for control purposes.

The rules are a good compromise between an understandable representation of knowledge and formal requirements. In cognitive science, rules are seen as components of information-processing processes.