drools-eclipse/org.drools.eclipse/src/main/java/org/drools/eclipse/editors/rete/model/ReteGraph.java
public boolean addChild(BaseVertex vertex) {
        if ( vertex != null && vertices.add( vertex ) ) {
            firePropertyChange( PROP_CHILD_ADDED,
                                null,
                                vertex );
            return true;
        }
        return false;
    }
public boolean addChild(BaseVertex vertex) {
        if ( vertex != null && vertices.add( vertex ) ) {
            firePropertyChange( PROP_CHILD_ADDED,
                                null,
                                vertex );
            return true;
        }
        return false;
    }
Add new BaseVertex to the graph

@param vertex

@return true, if vertex was added, false otherwise