As the discussion sparked by Jon Bosak's comparison of ebXML and SOAP at XML 2000 continues, a new specification for SOAP Messages with Attachments has been submitted to the W3C as a Note.

Bosak's remarks characterized ebXML as the more robust solution for electronic commerce, placing SOAP as the solution for simple, lightweight communication. This speech provoked questions on xml-dist-app as to whether the members of the W3C XML Protocol Working Group agreed with Bosak's viewpoints.

The resulting discussion focused on hopes of convergence between SOAP and the transport and packaging part of ebXML. One should not be overoptimistic in the short term however, as ebXML has a tight deadline to meet and is working to a tighter schedule than W3C XML Protocol.

One of the reasons why ebXML pursued their own route, outlined by David Burdett, was that:

In fact ebXML looked long and hard at using SOAP as the outer wrapper for its messages but the SOAP specifications available at the time did not support attachments and MIME which made encryption impossible and also made it difficult to transport aribtrary content without base 64 encoding it.

Proponents of convergence may then be heartened by the recent submission from Microsoft, HP, IBM, Oracle and others to the W3C. SOAP Messages with Attachments defines a binding for a SOAP 1.1 message to be carried within a MIME multipart/related message. Rules for using URI references to refer to bundled entities are specified.

In their response to the submission, the W3C refer to the group's charter and observe that direct handling of binary data is a low priority for the XML Protocol group. Given that, they note:

Reusing a similar, MIME-based, solution could be a low-cost option for the XML Protocol Working Group. The XML Protocol Working Group will determine whether, when, or how to incorporate this submission in their work.

Notwithstanding the "low priority," it seems essential that the W3C XML Protocol supports attachments in order to achieve convergence with ebXML. Sun, the only big-hitting vendor absent from the list of submitters of this note, is clearly, and with increasing emphasis, placing its bets on ebXML to become the widespread protocol for e-business.