The ebXML Registry is similar to UDDI in that it allows businesses to find one another, to define trading-partner agreements, and to exchange XML messages in support of business operations. The goal is to allow all these activities to be performed automatically, without human intervention, over the Internet. The ebXML architecture has many similarities to SOAP/WSDL/UDDI, and some convergence is taking place with the adoption of SOAP in the ebXML transport specification. RosettaNet also announced its adoption of the ebXML transport. The ebXML messaging specification is based on SOAP with Attachments, but does not use WSDL. ebXML does add security, guaranteed messaging, and compliance with business process interaction specifications.
The ebXML initiative is sponsored by the United Nations Centre for Trade Facilitation and Electronic Business (UN/CEFACT) and OASIS to research, develop, and promote global standards for the use of XML to facilitate the exchange of electronic business data. A major goal for ebXML is to produce standards that serve the same or similar purpose as EDI, including support for emerging industry-specific XML vocabularies.
More information: ebXML Registry page on the OASIS website
More on the general topic: Repository