According to the abstract, the spec says it defines a "binding or a SOAP
1.1 message to be carried within a MIME multipart/related." Later on it
uses "one or more" to talk about attachments, but there's nothing that
says an attachment is required. It uses language like "Referenced parts
must..." so if they're not referenced, then they needn't. :)
Personally, I think it's angels on pinheads. As Dale pointed out, the
underlying MIME spec allows one-part multipart. There is nothing in the
spec that says you can't use it. So go for it. But to be sure I sent
email to the authors asking for clarification.
I'm still in favor of always using one MIME format.
/r$
PS: Recalling the IP issues when ebXML adopted SwA, I like this quote
from the spec "In other words, we take a minimalist approach to show
what is already possible with existing standards without inventing
anything." :)
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