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Backwards compatibility and DOCTYPE

From: Bert Bos <bert@w3.org>
Date: Wed, 05 Mar 2008 01:02:47 +0100
Message-ID: <47CDE327.7040505@w3.org>
To: public-html-comments@w3.org

The HTML5 WD states (section 1.1.1[1]) that the format is meant to be as 
much backwards-compatible as possible. With a little change to section 
8.1.1[2], HTML5 could, in fact, be fully backwards compatible.

The current version (4.01) of HTML requires[3] documents to start with 
this DOCTYPE line:

     <!doctype html public "-//W3C//DTD HTML 4.01//EN"
     "http://www.w3.org/TR/html4/strict.dtd">

But that line is not allowed in the latest draft of version 5. Why not?

The corresponding DOCTYPE lines from earlier versions of HTML can also 
be allowed. I think most documents that conformed to HTML when those 
DOCTYPE lines were current are still valid in HTML5 (once HTML5 allows 
those DOCTYPEs.)

[1] http://www.w3.org/TR/2008/WD-html5-20080122/#relationship
[2] http://www.w3.org/TR/2008/WD-html5-20080122/#the-doctype
[3] http://www.w3.org/TR/1999/REC-html401-19991224/struct/global.html#h-7.2



Bert
-- 
   Bert Bos                                ( W 3 C ) http://www.w3.org/
   http://www.w3.org/people/bos                               W3C/ERCIM
   bert@w3.org                             2004 Rt des Lucioles / BP 93
   +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Wednesday, 5 March 2008 00:03:45 GMT

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