What are the legal grounds upon which the court relies in issuing a judgment in favor of the plaintiff in the event the defendant fails to appear or submit a defense after proper notification?

The court relies in issuing its judgment on the validity of the notification to the defendant, which is deemed valid if carried out in accordance with the statutory procedures, such as notification via authenticated electronic means. The proceedings are considered adversarial in presence if the defendant or their agent was personally notified, or if either of them appeared, or submitted a statement of defense, even if they subsequently failed to appear. Furthermore, an ordinary document is considered evidence against the person who signed it unless explicitly denied, which supports the establishment of the claimed rights.