DR612 - Normative binding to HTTP (incl. "pre-XP browser technology")

I believe the 2nd sentence should be deleted, as this is a requirement about
HTTP.  A non-exhaustive list of transports we do expect to address in
discussion should be elsewhere in this document, however.

I think it's clear we need more definition on the last sentence, and just
how browsers are expected to interact with XP technology.  One possible
use-case is in
http://lists.w3.org/Archives/Public/xml-dist-app/2000Nov/0098.html.

--Glen