Position of ebMS3 SOAP Root Part

[Pim van der Eijk <pvde@sonnenglanz.net>]

Hi,

According to R2929 of the WS-I attachments profile, which is referenced 
from the Basic Profile, which in turn is a normative reference in AS4,  
the SOAP root part does not have to be the first MIME part, as long as 
there is an HTTP MIME header "start" attribute that identifies the 
non-first MIME part containing the SOAP part, 
http://www.ws-i.org/Profiles/AttachmentsProfile-1.0.html#Ordering_of_MIME_Parts. 
So it seems that the ebMS3 SOAP header MIME part can be anywhere in the 
AS4 envelope.

Furthermore,  the HTTP Content-Length is not required and can be ignored 
according to 5.1.2.1 of ebMS3 Core.

Figure 8 in ebMS3 Core shows the SOAP root part as first MIME part, but 
this does not mean the SOAP root has to be the first part.

Taken together,  this suggest a sending MSH could start sending the 
message while the message body (compressed and/or signed and/or 
encrypted payloads) is still being created, because creation of the 
ds:SignedInfo containing the digests of payload parts can be postponed 
until all payloads are constructed and transmitted.

An implementer indicated this would allow them to optimize the sending 
of large AS4 messages.  I think in theory it should work, but I am 
wondering if AS4 products could handle this in practice, as receivers.   
If you have an AS4 implementation,  can you let me know if this would 
work in practice with your product?

Kind Regards,

Pim