This page:
http://www.loc.gov/standards/sru/resources/schemas.html

says:

"The Explain document lists the XML schemas for a given database in which records may be transferred. Every schemas is unambiguously identified by a URI and a server may assign a short name, which may or may not be the same as the short name listed in the table below (and may differ from the short name that another server assigns)."


But perusing the SRU/ZeeRex Explain documentation I've been able to find, I've been unable to find WHERE in the Explain document this information is listed/advertised. 

Can anyone clue me in?