I believe there has been an Internet-Draft written on this very topic
by Larry Masinter and Ernesto Nebel, "Form-based File Upload in HTML",
<draft-ietf-html-fileupload-01.txt>.
It specifies the ability to upload files using a form based mark-up,
it also includes the MIME encoding. They have an example
implementation for Mosaic, the code is accessible at
URL:ftp://parcftp.xerox.com/transient/file-upload/
"To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast)."
Hope this helps...
kipp
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Kipp Jones (kipp@cc.gatech.edu)(http://www.cc.gatech.edu/grads/j/Kipp.Jones/)
Graduate Research Assistant Computing and Networking Services
College of Computing, Room 212, Georgia Institute of Technology, Atlanta, GA
"Every thirty minutes, another network connects" Anthony-Michael Rutkowski