Drools was bought by JBoss and released as JBoss Rules. Drools is a rules engine that use the ReteOO and is based on the Rete algorithm.
There are very expensive rules engines available, but JBoss Rules is open source. It doesn’t provide some of the nicer features like a GUI editor for editing rules, but brings significant savings for those who are willing to forgo this.
Rules engines break out the logic rules and can sometimes allow changes to rules without need to modify the underlying code. Rules engines, in theory, allow non programmers to make changes to business logic without having to recompile the source code.
Drool rule syntax is not the easiest to read, but improvements have been made in the JBoss Rules Implementation. Drool originally used XML for rule definitions, but JBoss Rules supports multiple language formats with the ability to add more.
Drools was original a Java tool, but full .NET is provided with JBoss Rules.
JBoss notes JBoss rules features as:
Domain Specific Language
Logic and Data Separation
Speed and Scalability
Eclipse IDE pluging with intellisense, autocomplete and debugging
JBoss Rules is JSR 94 compliant, a Java Rule Engine API.
Enterprise rule engine alternatives are Fair Isaac’s Blaze Advisor and ILOG’s JRules.
An open source rule engine alternative is Sandia Labs’ Jess.
It sounds like JBoss Rules is making a big difference to Drools and a better one.