R.I. Gen. Laws § 9-5-20: Writs and other process against unknown defendant.

Whenever the name of any defendant or respondent is not known to the plaintiff, the summons and other process may issue against him or her by a fictitious name, or by such description as the plaintiff or complainant may select; and if duly served, it shall not be abated for that cause, but may be amended with or without terms as the court may order.