D.C. Code § 40-303.08
The proceeding to enforce the lien hereby given shall be a bill in equity, which shall contain a brief statement of the contract on which the claim is founded, the amount due thereon, the time when the notice was filed with the Recorder of Deeds, and a copy thereof served on the owner or his agent, if so served, and the time when the building or the work thereon was completed, with a description of the premises and other material facts; and shall pray that the owner's interest in the premises be sold and the proceeds of sale applied to the satisfaction of the lien. If such suit be brought by any person entitled, other than the principal contractor, the latter shall be made a party defendant, as well as all other persons who may have filed notices of liens, as aforesaid. All or any number of persons having liens on the same property may join in one suit, their respective claims being distinctly stated in separate paragraphs; and if several suits are brought by different claimants and are pending at the same time, the court may order them to be consolidated.
D.C. Code § 40-303.08
Service by publication on nonresidents, absent defendants, and unknown heirs or devisees, see § 13-336. .