A rules engine is a special software program that carries out one or more rules. The engine supports various functions. They might include preconditions, facts, etc. Nevertheless, there exists another definition. So, it is a string of production rules. In its turn, every rule has a condition and a rule. To understand the mechanism, let’s set the following description. For instance, there is a flow of data that flows through the system. The system picks the rules that fit the settled conditions. Therefore, the engine will evaluate the chosen actions.
There are different rules engine types. For example, business rules engines use the forward chaining principle. We can divide them into 2 classes.
The first one uses production rules. This rule covers the “if” – “then” conditions.
The second type employs the reaction condition. This rules engine interacts with the incoming processes.
Yet, there are backward chaining engines. The processing logic is reversed here. So, the engines seek the fact at first. The fact has to fit the goal. What’s interesting, some engines can switch between back- and forward chaining.
Also, there is a deterministic approach to rule engines. This kind may use both backward and forward chaining. The implementation and maintenance ease is the main advantage of this type.