following the rules of RFC1808, if the BASE is given by the
content-location of the first part, the relative URL contained inside
will identify the location below.
Following the rules of RFC 1808, the base URL for resolving relative
URLs within that message (including the content) can be defined
by a Base: header field in the message or message part. This does
apply in this situation, does apply to MIME, and seems to be ignored
in this discussion.
...Roy T. Fielding
Department of Information & Computer Science
(fielding(_at_)ics(_dot_)uci(_dot_)edu)
University of California, Irvine, CA 92717-3425 fax:+1(714)824-4056
http://www.ics.uci.edu/~fielding/