W3C home > Mailing lists > Public > public-html@w3.org > July 2008

Re: SVGWG SVG-in-HTML proposal (Was: ISSUE-41: Decentralized extensibility)

From: Ian Hickson <ian@hixie.ch>
Date: Tue, 29 Jul 2008 11:38:59 +0000 (UTC)
To: Sam Ruby <rubys@us.ibm.com>
Cc: Erik Dahlström <ed@opera.com>, Henri Sivonen <hsivonen@iki.fi>, Julian Reschke <julian.reschke@gmx.de>, HTML WG <public-html@w3.org>
Message-ID: <Pine.LNX.4.62.0807291123140.30692@hixie.dreamhostps.com>

On Tue, 29 Jul 2008, Sam Ruby wrote:
> 
> Not too long ago, the presumption was that trailing soliduses in tags 
> must always be treated as an error, lest the web would break.  This was 
> replaced by the assumption that trailing soliduses in all but a few, 
> well defined places would be treated as an error.

Indeed, I even mentioned that very case in the e-mail to which you 
replied:

| Sometimes one agrees with the choice, and sometimes one doesn't, e.g. 
| as I don't in the issue of including XML-like syntactic placebos in 
| text/html. That's just the way the chips fall.

We have to base our decisions on evidence, not our wishes.


> Yes, some people here have the assumption that namespace prefixes must 
> always be treated as an error, lest the web would break.

Note that this isn't really a technically similar case. The placebo syntax 
in text/html does nothing at all -- it's just allowed so as to reduce 
author confusion. Namespace prefixes _do_ have a practical effect, so it's 
not just about whether they're allowed or not, it's about whether they are 
supported or not.

Evidence suggests that they cause great author confusion (e.g. [1]). In 
addition, specific syntax like XML's wouldn't work in text/html due to the 
problem you mention (the undesired effect on legacy content). We have to 
balance these two relativel major negatives against the benefits of 
prefixes. These are basically limited to the ability to mix multiple 
vocabularies in a very interleaved fashion. Since there really is no need 
to do this in HTML, at least so far, the negatives strongly outweigh the 
positives. (Note that here I'm talking specifically about namespace 
_prefixes_ and their associated declarations, and not namespaces in 
general. There are many ways of designing namespace syntax, and many do 
not use any kind of indirection like prefixes.)

As I said, these issues were studied years ago, and underlie much of 
HTML5's design. There isn't really much point discussing the issue unless 
some radical new evidence has come up since the 2003/2004 timeframe.


[1] "As the author of an O'Reilly book on XForms, I can report that 90% of 
the technical questions from readers involve confusion related to 
namespaces."
  -- http://www.w3.org/2004/04/webapps-cdf-ws/papers/verity.html

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Tuesday, 29 July 2008 11:39:34 UTC

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