a) document format. Although IPP is a nice interoperable
protocol, one person's IPP server won't necessarily do the
right thing with another person's IPP client's documents
unless there's a little more care played with
printer-formats-supported. I think what you really
need for guaranteed interoperability is:
1) a minimum format that everyone is guaranteed to understand
(TIFF profile S, anyone?)
2) some better way of the sender determining recipient
capabilities (printer-features using CONNEG syntax, anyone?)
b) sender and recipient identification. Although IPP has some
features that might be used for these, you won't have interoperability
until you standardize on their use. You need:
1) sender identification. While the 'authentication'
used for authorization to use the printer might serve
as an identification, sometimes it doesn't. You need
to clearly say which parts of IPP are supposed to be
used for "who is this from", and encourage the use
of this material on the cover sheet.
2) recipient identification. Maybe this is the "user name"?
The problem is that with "printing" the "sender" is usually
the same as the "recipient". You know, I "print" something
by "e-print"ing it to myself. But I think IPP has only one
user field, whereas if you're going to use it for
communication, you need two.
So, before going off into too many more flights of fancy about
internet printing, could you focus a bit on the issues that
were labelled "IPP2FAX" before?