Except as may be otherwise provided in this chapter, any party may take the testimony of any person, including a party, by deposition upon oral examination or written interrogatories for use as evidence in the proceeding, except that leave must be obtained if notice of the taking is served by a proponent within twenty days after the filing of a complaint. The attendance of witnesses may be compelled by the use of a subpoena. Depositions shall be taken only in accordance with this rule and the rule of subpoenas.