RE: Describing which blobs are to be optimized.

My reading of the straw polls [1] relative to Issue 207 leads me to
suggest the following resolution:

Ask the XMLP WG to augment the paragraph in MTOM
[http://www.w3.org/TR/soap12-mtom/#aof-sending] as indicated {{thus}}:

"Note: the means of identifying element information items that contain
base64 encoded data in canonical lexical form are
implementation-dependent. Some implementations can identify such element
information items by construction (e.g., because a certain API may
create only canonical forms); others may check the characters prior to
sending{{, others may rely on information in the description such as the
presence and/or value of the xmlmime:expectedMediaType schema annotation
[reference to XMLMIME]}}.  Because of the need to exactly preserve the
characters in the transmitted Infoset, non-canonical representations
MUST NOT be optimized."

 [1] http://lists.w3.org/Archives/Public/www-ws-desc/2004Jun/0128.html

P.S.  for XMLP: It's a bit disconcerting to see a "MUST NOT" in a
"Note".