[whatwg] Create my own DTD and specify in DOCTYPE? Re: Validation

Darxus at ChaosReigns.com Darxus at ChaosReigns.com
Tue Jul 21 12:21:40 PDT 2009

Am I correct in concluding that my best option is to create my own
HTML5 DTD, and use a DOCTYPE along the lines of:

<!DOCTYPE html SYSTEM "http://www.chaosreigns.com/DTD/html5.dtd">


Can the HTML5 spec be modified slightly to say that this sort of thing
( http://dev.w3.org/html5/spec/Overview.html#the-doctype )

It seems like if I do create a DTD, I should not permit copying, in order
to increase the number of individually created DTDs to check against each

I'm also open to the possibility of HTML5 specifying some sort of comment
stating the HTML version number.

Reasons for the above conclusion:

An official HTML5 DTD is not desired because official schemas are buggy and
people don't fix them, and having only non-official DTDs will improve
quality, according to Ian Hixie, March 2009 -

Also, there does not appear to be an XML 1.0 conformant way to specify more
than <!DOCTYPE html> (which conforms) without specifying a url for a DTD.

The bit in quotes is a Public Identifier, which is the entire contents
of RFC3151: http://www.ietf.org/rfc/rfc3151.txt

And the full spec is in ISO 8879:1986 (SGML) which costs US$ 222.525,
so I don't know what the Public Text Class ("NONE" above) could be
replaced with, other than "ENTITIES".

Another use that occurred to me is the case where someone has thousands of
html files, which they want to automatically validate at once, and some of
them have been updated to a more recent standard (and they want to make
sure they stay compliant with it), but others have not been dealt
with yet.

On 07/21, Philip Taylor wrote:
> <!DOCTYPE html SYSTEM "6"> as the shortest string that provides a

Violates XML 1.0 and RFC3151 (Public Identifier).

> If you want to check that your pages are compatible with certain
> browser releases, the language version number is a very bad
> approximation - you'd want a tool that understands what features IE10
> supports (maybe some (but not all) from HTML4, some (but not all) from

Indeed.  Do you have that information?  If not, I would still like the
option of noting a version type in my documents.

Although the possibility of creating a DTD based on what conforms to
standards *and* current browsers are capable of is a fun idea.

> like <meta name="check-ua-compatibility" content="ie=10;fx=5"> seems a


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to air...useful against soft targets such as...armored vehicles...and
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