Proposed resolution for issue 440

On the call today we discussed issue 440[1] which asks 

1. 	whether MTOM packages can contain MIME body parts that are NOT
referenced by an xbinc:Include element
2.	whether a MIME body oart can be referenced by multiple
xbinc:Include elements

I took an action to propose a resolution to this issue, so here it is.

Proposed resolution:

Each MIME body part (except the root) MUST be referenced by exactly one
xbinc:Include element. Intermediaries are required to respect this rule.

Rationale:

Allowing MIME parts that are unreferenced breaks the infoset model.
Ensuring MIME parts are referenced exactly once simplifies
implementations.

Cheers

Gudge

[1] http://www.w3.org/2000/xp/Group/xmlp-issues.html#x440