function createSubComponent() {
    $output = null;
    foreach( $this->components as $component ) {
      if( '' >= $component->getConfig( 'language'))
        $component->setConfig( 'language',  $this->getConfig( 'language' ));
      $component->setConfig( 'allowEmpty',  $this->getConfig( 'allowEmpty' ));
      $component->setConfig( 'nl',          $this->getConfig( 'nl' ));
      $component->setConfig( 'unique_id',   $this->getConfig( 'unique_id' ));
      $component->setConfig( 'format',      $this->getConfig( 'format' ));
      $output .= $component->createComponent( $this->xcaldecl );
    }
    return $output;
  }