I am please to share that the ebXML RegRep TC published the latest
draft of RegRep 4 specifications:
http://lists.oasis-open.org/archives/regrep/201003/msg00018.html
The RegRep TC is interested in feedback on its latest specifications.
The ebXML RegRep 4 WD5 specifications have been implemented
by Wellfleet
Software's WellGEO RegRep product which has been deployed at several major institutions.