W3C home > Mailing lists > Public > public-html@w3.org > October 2009

Re: ISSUE-55: Re-enable @profile in HTML5 (draft 1)

From: Jonas Sicking <jonas@sicking.cc>
Date: Sun, 11 Oct 2009 00:17:52 -0700
Message-ID: <63df84f0910110017q7eea876rfc021aa26814b3ea@mail.gmail.com>
To: Manu Sporny <msporny@digitalbazaar.com>
Cc: HTMLWG WG <public-html@w3.org>
On Sat, Oct 10, 2009 at 12:43 PM, Manu Sporny <msporny@digitalbazaar.com> wrote:
> Jonas Sicking wrote:
>> On Tue, Sep 29, 2009 at 12:33 AM, Toby Inkster <tai@g5n.co.uk> wrote:
>>> On Mon, 2009-09-28 at 17:32 -0700, Jonas Sicking wrote:
>>>> I would personally recommend that RDFa follow the strategy that HTML
>>>> uses
>>> To only provide version identifiers for the first four versions?
>>
>> To never break backwards compatibility with existing content. The
>> "version identifiers" in earlier versions of HTML were never, to my
>> knowledge, used as a way to break compatibility with older versions of
>> the specification.
>
> I think you're missing Toby's point. Let me attempt to elaborate in
> order to shed some light on the issue.
>
> At present, your statement that HTML5 will "never break backwards
> compatibility with existing content" is not true. HTML5 breaks backward
> compatibility in many (good) ways... it obsoletes a number of HTML features:
>
> http://dev.w3.org/html5/spec/Overview.html#non-conforming-features

But all these features still work. HTML5 doesn't actually change
behavior of anything (other than when previous versions of HTML
doesn't match reality).

> Now, I don't know the intent of the Non-conforming features section, but
> after reading Section 12.2, if I were to write a User Agent - I expect
> that I wouldn't have to support any of those features. For example, if
> my web browser saw <center>, it would ignore it completely and be fully
> conformant with the HTML5 specification, IIRC.

I wouldn't expect that to be the case. The requirements on
implementations doesn't mention anything as being optional [1]

http://dev.w3.org/html5/spec/Overview.html#requirements-for-implementations

And more importantly, if you care about supporting existing HTML
pages, you do need to render the contents of <center> elements
centered.

> Since most HTML4 documents are now magically HTML5 documents, how does
> this not break backward compatibility in this particular scenario?

By not changing the processing requirements for any of these features.

Like I said, I personally think it's a really bad idea as it'll cause
a lot of confusion and complexity for authors. It'll mean that content
can't be copied reliably between documents. It'll mean that all code
that generates content will have to know which version to generate
content for.

But ultimately, if RDF and/or RDFa wants to change in a backwards
incompatible ways that is of course up to the developers of those
specifications.

/ Jonas
Received on Sunday, 11 October 2009 07:18:47 UTC

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