Overview (Knowledge API Legacy5 Adapter 6.2.0.Final-redhat-14 API)

Packages
Package	Description
org.drools	The KnowledgeBase and its factory.
org.drools.base
org.drools.builder	The builder package is responsible for building knowledge definitions from artifact resources.
org.drools.builder.conf
org.drools.builder.help	Providers helper classes that can be used during building.
org.drools.command
org.drools.command.impl
org.drools.concurrent
org.drools.conf
org.drools.definition	All classes to create definitions, as built by the KnowledgeBuilder from artifact resources, can be found here.
org.drools.definition.process	The classes that make up a Process definition.
org.drools.definition.rule	The classes that make up a Rule definition.
org.drools.definition.type
org.drools.event	Drools has a comprehensive event api for all parts of the platform.
org.drools.event.io
org.drools.event.knowledgeagent
org.drools.event.knowledgebase	Events emitted while updating the definitions in the KnowledgeBase.
org.drools.event.process	Events emitted while process instances are executing.
org.drools.event.rule	Events emitted while Rules are executing.
org.drools.impl
org.drools.impl.adapters
org.drools.io	io library for working with Resources See ResourceFactory for more details
org.drools.logger	Logger classes use to log the KnowledgeRuntime's execution.
org.drools.management
org.drools.marshalling	Marshalling classes are used to marshall and unmarshal StatefulKnowledgeSessions See MarshallerFactory for more detailed information.
org.drools.osgi.api
org.drools.persistence.jpa
org.drools.runtime	The runtime engine classes, including StatefulKnowledgeSession and StatelessKnowledgeSession.
org.drools.runtime.conf
org.drools.runtime.help
org.drools.runtime.process	The process runtime classes.
org.drools.runtime.rule	The rule runtime classes.
org.drools.task.service
org.drools.time	Classes related to Time in Drools.
org.drools.util

Drools & jBPM provide an knowledge-centric API, where rules and processes are first class citizens.

The most common interfaces you will use are:

org.drools.core.builder.KnowledgeBuilder
org.drools.KnowledgeBase
org.drools.agent.KnowledgeAgent
org.drools.core.runtime.StatefulKnowledgeSession
org.drools.core.runtime.StatelessKnowledgeSession

Factory classes, with static methods, provide instances of the above interfaces. A pluggable provider approach is used to allow provider implementations to be wired up to the factories at runtime. The Factories you will most commonly used are:

org.drools.core.builder.KnowledgeBuilderFactory
org.drools.io.ResourceFactory
org.drools.KnowledgeBaseFactory
org.drools.agent.KnowledgeAgentFactory

A Typical example to load a rule resource.

KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add( ResourceFactory.newUrlResource( url ),
                      ResourceType.DRL );
if ( kbuilder.hasErrors() ) {
    System.err.println( builder.getErrors().toString() );
}                     

KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
kbase.addKnowledgePackages( builder.getKnowledgePackages() );

StatefulKnowledgeSession ksession = knowledgeBase.newStatefulKnowledgeSession();
ksession.insert( new Fibonacci( 10 ) );
ksession.fireAllRules();

ksession.dispose();

A Typical example to load a process resource. Notice the ResourceType is changed to BPMN2 in this example.

KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add( ResourceFactory.newUrlResource( url ),
              ResourceType.BPMN2 );
KnowledgeBase kbase = kbuilder.newKnowledgeBase();
StatefulKnowledgeSession ksession = knowledgeBase.newStatefulKnowledgeSession();
ksession.startProcess( "Buy Order Process" );
ksession.dispose();

'kbuilder', 'kbase', 'ksession' are the variable identifiers often used, the k prefix is for 'knowledge'.

It is also possible to configure a KnowledgeBase using configuration, via a xml change set, instead of programmatically. Here is a simple change set:

<change-set xmlns='http://drools.org/drools-5.0/change-set'
           xmlns:xs='http://www.w3.org/2001/XMLSchema-instance'
           xs:schemaLocation='http://drools.org/drools-5.0/change-set change-set-5.0.xsd' >
  <add>
    <resource source='classpath:org/domain/someRules.drl' type='DRL' />
    <resource source='classpath:org/domain/myProcess.bpmn2' type='BPMN2' />
  </add>
</change-set>

And it is added just like any other ResourceType

KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add( ResourceFactory.newUrlResource( url ),
              ResourceType.ChangeSet );

The majority of knowledge API is considered stable and should not change, experimental classes and API's will be marked as such.