|Stable release||5.5.0 / November 13, 2012|
Drools is a business rule management system (BRMS) with a forward chaining inference based rules engine, more correctly known as a production rule system, using an enhanced implementation of the Rete algorithm.
Drools supports the JSR-94 standard for its business rule engine and enterprise framework for the construction, maintenance, and enforcement of business policies in an organization, application, or service.
Drools is a rules engine implementation based on Charles Forgy's Rete algorithm tailored for the Java language. Adapting Rete to an object-oriented interface allows for more natural expression of business rules with regard to business objects. Drools is written in Java, but able to run on Java and .NET.
JBoss Rules 
JBoss Rules is a reasoning engine that includes a forward chaining rule engine based on Drools. JBoss Rules is the productised version of Drools; this means it comes with support that will last several years for that particular branch, with bug and essential feature back ports. For a time the Drools name was dropped in an attempt to fully establish the JBoss Rules brand as both the project and the product; however, two years later, the community was mostly still calling it Drools, so the name was reclaimed by the community for the project. The product name remains JBoss Rules.
JBoss Enterprise BRMS 
JBoss Enterprise BRMS is a business rule management system and reasoning engine for business policy and rules development, access, and change management. JBoss Enterprise BRMS is a productized version of Drools with enterprise-level support available. JBoss Rules is also a productized version of Drools, but JBoss Enterprise BRMS is the flagship product.
Components of the enterprise version:
- JBoss Enterprise Web Platform – the software infrastructure, supported to run the BRMS components only
- JBoss Enterprise Application Platform or JBoss Enterprise SOA Platform – the software infrastructure, supported to run the BRMS components only
- Business Rules Engine – Drools Expert using the Rete algorithm and the Drools Rule Language (DRL)
- Business Rules Manager – Drools Guvnor - Guvnor is a centralised repository for Drools Knowledge Bases, with rich web based GUIs, editors, and tools to aid in the management of large numbers of rules.
- Business Rules Repository – Drools Guvnor
Drools and Guvnor are JBoss Community open source projects. As they are mature, they are brought into the enterprise-ready product JBoss Enterprise BRMS.
Components of the JBoss Community version:
- Drools Guvnor (Business Rules Manager) – a centralized repository for Drools Knowledge Bases
- Drools Expert (rule engine) – uses the rules to perform reasoning
- Drools Flow (process/workflow), or jBPM 5 – provides for workflow and business processes
- Drools Fusion (event processing/temporal reasoning) – provides for complex event processing
- Drools Planner (automated planning) – optimizes automated planning, including NP-hard planning problems
This example illustrates a simple rule to print out information about a holiday in July. It checks a condition on an instance of the Holiday class, and executes Java code if that condition is true.
rule "validate holiday" dialect "mvel" when h1 : Holiday( when == "july" ) then System.out.println(h1.name + ":" + h1.when); end
Related systems 
- CLIPS: public domain software tool for building expert systems.
- JESS: a rule engine for the Java platform - it is a superset of CLIPS programming language.
- Prolog: a general purpose logic programming language.
- OpenL Tablets: business centric rules and BRMS.
- DTRules: a Decision Table based, open-sourced rule engine for Java.
- Oracle Policy Automation: a suite of software products for modeling and deploying business rules within enterprise applications
See also 
- "JBoss Enterprise BRMS". Red Hat.
- "JBoss Enterprise BRMS: Answers to frequently asked questions". JBoss Community.
- "JBoss Enterprise BRMS Platform 5.1". Red Hat.
- "JBoss Enterprise BRMS datasheet". Red Hat. p. 4.
- "Drools 5 - The Business Logic integration Platform". JBoss Community.
- Drools 2.0 Codehaus site
- Drools Sourceforge site
- Drools Blog
- JBoss Rules
- Bob McWhirter
- Mark Proctor
- JBoss Drools vs JBoss Rules
- Implementing business logic with Drools
- Give your business logic a framework with Drools
- Drools wiki
- Article on Seam security with JBoss Rules
- Other open source projects based on Drools 5
- Realtime intelligence using Drools Fusion
- Drools State of the Union presentation at JBossWorld 2009
- Drools Rule editor in Flex
- Drools with Spring Tutorial using the JSR-standard