Drools

Rule systems are able to solve hard problems by providing the detail of the arrival of the solution and also why every decision was been taken along the way.

Major benefits of Rule Engine are:

Logic & Data Separation
To break down the domain objects from business rules could make it possible to easily maintain the application. This is possible because it may shield from the future alterations.

Speed & Scalability
Several times, “if” condition is applied this is not actually needed. The Rete algorithm makes the replacement of all “ifs”…(as implemented by Drools) and then statements along with a network that is optimized.

Knowledge Centralization
Repository of knowledge is created by using the rules. For business policy, it could be the single point of truth. Rules are ideally so readable that they might serve the purpose of documentations.

Tool’s Integration
To write the rules actually means to be accustomed to the Rule debugging, validation and language. Eclipse is found to give an excellent delivery tool which tests your rules.