The rule engine is the computer program that delivers KRR(Knowledge Representation And Reasoning) functionality to the developer.
The term "rules engine" is quite ambiguous in that it can be any system that uses rules, in any form, that can be applied to data to produce outcomes. This includes simple systems like form validation and dynamic expression engines.
Drools started life as a specific type of rule engine called a Production Rule System (PRS) and was based around the Rete algorithm
Drools 5.x implements and extends the Rete algorithm. This extended Rete algorithm is named ReteOO , signifying that Drools has an enhanced and optimized implementation of the Rete algorithm for object oriented systems. Drools 6.x introduces a new lazy algorithm named PHREAK.
Comparing the merits of forward chaining (reactive and data driven 响应和数据驱动) or backward chaining (passive query 被动查询). Here is a quick explanation of these two main types of reasoning.
