A business rules engine is a software system that helps manage business rules. The rules a business follows may come from legal regulation ("An employee can be fired for any reason or no reason but not for an illegal reason"), company policy ("All customers that buy more than $100 at one time will receive a 10% discount") or other sources. The Rule Engine software, among other functions, may help to register, classify and manage all these rules; verify consistence of formal rules ("Flooring material must be flattish to ease cleaning" is inconsistent with "flooring material must be rough to avoid slipping"); infer some rules based on other rules; and relate some of these rules to Information Technology applications that are affected or need to enforce one or more of the rules. Rules can also be used to detect interesting business situations automatically. For example, "notify sales when inventory is lower than 10 and we have more than 5 pending orders on a Monday."

IT use

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For any IT application, the business rules change more frequently than the rest of the application code. Rules Engines or Inference Engines are the pluggable software components that separate the business rules from the application code. This allows the business users to modify the rules frequently without the need of IT intervention and hence allowing the applications to be more adaptable with the dynamic rules.

In previous generation applications, data was meant to be dynamic which was supposed to be operated upon by the logic and rules to get the desired results. Data Dynamics are no longer the only need of the hour but the focus has been shifted to the dynamic rules.

Design strategies

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There is a range of rule engine design strategies available--from custom language-based interpretive approaches to XML-based code generation approaches.

Types of rule engines

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There are mainly two different types of rule engines. The first one is rule engines with so-called production/inference rules. These types of rules are used to answer complex questions and infer answers. For example, such a rule could answer the question: "Should this customer be allowed a mortgage?".

The other type of rule engine is those implementing reaction rules. The reactive rule engines are used to detect and react to interesting patterns of events occurring. For example a reactive rule engine could be used to alert a manager when certain items are out of stock.

The biggest difference between these types is that rule engines with production rules answer questions when a user or application submits them. A reactive rule engine reacts automatically when a certain rule is violated and sounds an alarm.

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Business Rules Engine Providers

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Here is a list of Rules Engines

QuickRules Java and .NET Rules Engine QuickRules Business Rules Management System (BRMS) helps enterprises to separate and externalize business rules from the application code. With an integrated development and deployment environment, the QuickRules BRMS provides the tools required to write, edit, and test business rules.

InRule .NET Rules Engine InRule provides technology for the authoring, management and verification of application decision logic that involves rules, calculations and dynamic user interfaces. InRule's declarative development approach captures business intent by allowing users to encode rules without the overhead of custom programming, which results in highly adaptive business processes. InRule's evolving "rules console" approach utilizes a rules catalog that provides visibility into core logic and facilitates sharing that logic across applications.

Versata Rules Engine Versata’s products are used to build applications, components and services for J2EE and SOA architectures using declarative business rules.

Jess Java Rules Engine Jess is a rule engine and scripting environment written entirely in Sun's JavaTM language by Ernest Friedman-Hill at Sandia National Laboratories in Livermore, CA. Using Jess, you can build Java software that has the capacity to "reason" using knowledge you supply in the form of declarative rules. Jess is small, light, and one of the fastest rule engines available. Its powerful scripting language gives you access to all of Java's APIs.