Drools 2.1

Drools is a Rules Engine implementation based on Charles Forgys Rete algorithm tailored for the Java language. Adapting Rete to an object-oriented interface allows for more natural expression of business rules with regards to business objects. Drools is written in Java, but able to run on Java and .Net.
Drools is designed to allow pluggeable language implementations. Currently rules can be written in Java, Python and Groovy. More importantly, Drools provides for Declarative Programming and is flexible enough to match the semantics of your problem domain with Domain Specific Languages (DSL) via XML using a Schema defined for your problem domain.
DSLs consist of XML elements and attributes that represent the problem domain.
Enhancements:
Bug
- DROOLS-294 - WorkingMemory synchronization is not complete (Barry Kaplan)
- DROOLS-314 - MethodMetadataSources need a stopping Class (Barry Kaplan)
- DROOLS-318 - WorkingMemoryEventListenerProcessor implements wrong interface (Barry Kaplan)
- DROOLS-347 - Maven build of drools-spring-jdk5 fails on Mac OS X (Andy Barnett)
- DROOLS-367 - Wrong rule executed when modifying object in workingmemory (Michael Neale)
- DROOLS-374 - Caching of classloaders in causes problems with hot deployment in some J2EE containers (Michael Neale)
- DROOLS-376 - Make source file (c) headers consistent with codehaus (Michael Neale)
- DROOLS-386 - Bug with the Escalation example? (Robert Laflamme)
- DROOLS-401 - Missing semaphore types in schema file (rules.xsd) (Edson Tirelli)
- DROOLS-403 - no-loop incorrectly removes all instances of a rule from the agenda (Michael Neale)
- DROOLS-409 - rename getNoLoop to isNoLoop to obey JavaBean naming convention (Mark Proctor)
- New Feature
- DROOLS-303 - Default rule-method parameter annotation (Barry Kaplan)
- DROOLS-360 - Maven goal for drools-all-src-XXX.zip (Mark Proctor)
- DROOLS-361 - Auto add RuleSet to RuleBase (Barry Kaplan)
- DROOLS-363 - Decision tables in spreadsheets (Michael Neale)
- DROOLS-383 - Integrate java:functions feature in decision tables. (Michael Neale)
- DROOLS-388 - Support for application data (variables), per rule duration, salience and names (Ricardo Rojas)
- DROOLS-408 - Xor Group so only one rule can fire for a specific group (Mark Proctor)
Improvement
- DROOLS-296 - Allow for default id value in parameter annotations (Barry Kaplan)
- DROOLS-297 - Allow multiple consequence annotations per rule (Barry Kaplan)
- DROOLS-301 - Remove Drools prefix from annotations (Barry Kaplan)
- DROOLS-309 - MethodMetadataSource to ignore certain classes (Barry Kaplan)
- DROOLS-310 - Condition sharing for POJO rules (Peter Royal)
- DROOLS-348 - JDK 1.3 no longer supported (Barry Kaplan)
- DROOLS-350 - Utilize 1.4 nested exceptions (Barry Kaplan)
- DROOLS-357 - Packaging between factory and meta needs some attention (Barry Kaplan)
- DROOLS-364 - Update spring libs and config files for 1.2 (Barry Kaplan)
- DROOLS-372 - Update Groovy to JSR-03 (Mark Proctor)
- DROOLS-381 - Add object-condition tests to RuleBuilderTest (Barry Kaplan)
- DROOLS-387 - add ability for a DSL to acces the XML namespace information in a Configuration (James Strachan)
- DROOLS-402 - Refactor maven.xml and drools:dist to make it faster and more intelligent (Mark Proctor)
- DROOLS-410 - Update Janino to 2.3.8 (Mark Proctor)
Test
- DROOLS-346 - Ant build.xml doesnt run drools-jsr94 unit tests (Andy Barnett)
- Task
- DROOLS-351 - Remove drools-annotation and derivitives from 2.1 (Barry Kaplan)
- DROOLS-370 - Add in drools-decisiontables subproject (Michael Neale)