Levels"Daniel W. Connolly" <email@example.com>
Date: Fri, 10 Jun 1994 15:06:28 -0500
From: "Daniel W. Connolly" <firstname.lastname@example.org>
[I'm not sure why I don't just stick this in the spec and see what
folks think, but somehow it's easier for me to just brain-dump
to this archive for now...]
The idea is that if you write:
<!DOCYTYPE HTML "-//W3O//DTD WWW HTML 2.0//EN">
then that includes IMG, FORMS, and all the other current practice stuff.
I'm not sure when levels 0 and 1 will be completely specified, but
the idea is that you might write:
<!DOCYTYPE HTML "-//W3O//DTD WWW HTML 2.0//EN//Level 0">
<!DOCYTYPE HTML "-//W3O//DTD WWW HTML 2.0 Level 0//EN">
to indicate that you're not using any level 1 or level 2 features,
and a validating tool should report errors if you do.
As for how it works in practice, if a client says:
we specify that this means the same thing as
Accept: text/html; level=2
However, if it says:
Accept: text/html; level=0
(as, for example, the linemeode browser should) then it is an error
for a server to send a document containing IMG or FORM elements.
["It is an error" used here as by Guy Steele in his specs meaning
"the behaviour in that case is undefined."]
This allows the negotiation we've seen where a document says "click
_here_ if you grok forms, and _here_ if you don't" or "use _this_
index if you don't grok images" to be handled by the HTTP protocol.