Sun recommends using the Apache SOAP implementation, which is a very true implementation of the SOAP V1.1 specification. The UDDI V1 specification defines SOAP APIs. The XP Working Group is using the SOAP 1.1 specification as a starting point. The process is open to anyone who wants to participate. Currently there are more than 2000 companies, organizations, institutions, standards bodies, and individuals from all over the world participating in the effort.
SOAP defines a messaging protocol.
SOAP is a generic protocol that can be used for a wide variety of applications. You can certainly build a QoS-enabled international trade framework on top of SOAP, but the point is, you really only want to build that framework once, and then you want to get the international trade community to adopt it. The ebXML TRP team has looked at SOAP V1.1 and determined that the specification does not support certain technical requirements. Given that SOAP is not an internationally recognized official standard, and that it doesn't effectively support the ebXML technical requirements, ebXML TRP elected not to adopt SOAP, and it defined a different messaging protocol that used multipart MIME headers. In time this discussion will likely become moot.