> MIME type would seem to provide a most adequate filtering hook for IPP
> and other protocols which also wish to ride on http.
Filtering is not the issue with ipp: vs http:.
The problem with using http: for printers is that it hides the fact
that the resource is a printer. Users then have to keep track of
that information separately, while user agents (web clients etc.)
are unable to take advantage of the fact that the resource is a
printer to improve their user interfaces.
Keith