drools/drools-core/src/main/java/org/drools/core$ vi impl/KnowledgeBaseImpl.java

    public KnowledgeBaseImpl(final String id,
                             final RuleBaseConfiguration config) {
        this.config = (config != null) ? config : new RuleBaseConfiguration();
        this.config.makeImmutable();

        createRulebaseId(id);

        this.rootClassLoader = this.config.getClassLoader();

        this.pkgs = new HashMap<String, InternalKnowledgePackage>();
        this.processes = new HashMap<String, Process>();
        this.globals = new HashMap<String, Class<?>>();

        this.classTypeDeclaration = new HashMap<String, TypeDeclaration>();

        this.classFieldAccessorCache = new ClassFieldAccessorCache(this.rootClassLoader);
        kieComponentFactory = getConfiguration().getComponentFactory();

        this.factHandleFactory = kieComponentFactory.getFactHandleFactoryService();
        kieComponentFactory.getTraitFactory().setRuleBase(this);
        kieComponentFactory.getTripleStore().setId(id);

        setupRete();

        if ( this.config.getSessionCacheOption().isEnabled() ) {
            sessionsCache = new SessionsCache(this.config.getSessionCacheOption().isAsync());
        }

        sessionConfiguration = new SessionConfigurationImpl( null, this.config.getClassLoader(), this.config.getChainedProperties() );
    }

call setupRete()

    protected void setupRete() {
        this.rete = new Rete( this );
        this.reteooBuilder = new ReteooBuilder( this );

        NodeFactory nodeFactory = kieComponentFactory.getNodeFactoryService();

        // always add the default entry point
        EntryPointNode epn = nodeFactory.buildEntryPointNode(this.reteooBuilder.getIdGenerator().getNextId(),
                                                             RuleBasePartitionId.MAIN_PARTITION,
                                                             this.getConfiguration().isMultithreadEvaluation(),
                                                             this.rete,
                                                             EntryPointId.DEFAULT);
        epn.attach();

        BuildContext context = new BuildContext(this);
        context.setCurrentEntryPoint(epn.getEntryPoint());
        context.setTupleMemoryEnabled(true);
        context.setObjectTypeNodeMemoryEnabled(true);
        context.setPartitionId(RuleBasePartitionId.MAIN_PARTITION);

        ObjectTypeNode otn = nodeFactory.buildObjectTypeNode(this.reteooBuilder.getIdGenerator().getNextId(),
                                                             epn,
                                                             ClassObjectType.InitialFact_ObjectType,
                                                             context);
        otn.attach(context);
    }

drools/drools-core/src/main/java/org/drools/core$ vi reteoo/ReteooBuilder.java

    /**
     * Construct a <code>Builder</code> against an existing <code>Rete</code>
     * network.
     */
    public ReteooBuilder( final InternalKnowledgeBase  kBase ) {
        this.kBase = kBase;
        this.rules = new HashMap<String, BaseNode[]>();
        this.queries = new HashMap<String, BaseNode[]>();
        this.namedWindows = new HashMap<String, WindowNode>();

        //Set to 1 as Rete node is set to 0
        this.idGenerator = new IdGenerator();
        this.ruleBuilder = kBase.getConfiguration().getComponentFactory().getRuleBuilderFactory().newRuleBuilder();
    }