This Recommendation | International Standard defines a generic registration-hierarchical-name tree and the specific form of this RH-name tree called an ASN.1 Object Identifier (OID) tree, including registration of the top-level arcs of the OID tree. It specifies procedures that are referenced by other parts of the ITU-T Rec. X.660 series | ISO/IEC 9834 multi-part standard for the operation of International Registration Authorities.