parent::afterDelete(); 疑问 [ 新手入门 ]

/**
 * This is invoked after the record is deleted.
 */
protected function afterDelete()
{
    parent::afterDelete();
    Comment::model()->deleteAll('post_id='.$this->id);
    Tag::model()->updateFrequency($this->tags, '');
}

这是blog 的Post模型里的代码，这里调用父类的afterDelete方法的用意是什么？ 高手请赐教