Extensible Provisioning Protocol Subscription Mapping
An expired I-D that appears to have never been submitted to the IETF, or at least I can’t search for a canonical copy of it on tools.ietf.org. From the introduction:
This document describes a service subscription mapping for version 1.0 of the Extensible Provisioning Protocol (EPP). This mapping is specified using the Extensible Markup Language (XML) 1.0 as described in [XML] and XML Schema notation as described in [XMLS-1] and [XMLS-2]. However, notification or delivery methods for subscription services are not covered by this document.
Neustar’s EPP servers expose this, but its use looks to be essentially undocumented. I should probably whine at somebody there to figure out if it’s any use or just a legacy thing.