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Re: "HTML5 microsyntaxes instead of XSD datatypes"

From: Henri Sivonen <hsivonen@iki.fi>
Date: Wed, 2 Apr 2008 22:35:33 +0300
Cc: Geoffrey Sneddon <foolistbar@googlemail.com>, Henry Thompson <ht@w3.org>, Sandro Hawke <sandro@w3.org>, www-archive <www-archive@w3.org>, "Michael(tm) Smith" <mike@w3.org>
Message-Id: <80B6A7BD-7FCE-4E06-8D18-A7711840F3B1@iki.fi>
To: Dan Connolly <connolly@w3.org>

On Apr 2, 2008, at 21:41, Dan Connolly wrote:
> On Wed, 2008-04-02 at 19:13 +0100, Geoffrey Sneddon wrote:
>> On 2 Apr 2008, at 18:53, Dan Connolly wrote:
>>> Please help me remember to follow up; i.e. find
>>> test cases that distinguish the two designs and find out
>>> what requirements, if any, motivate the differences.
>> Sorry for jumping in on this like this (I saw this on -archive), but
>> the answer is the normal one: there is a large amount of content that
>> relies on the existing algorithms. There are known bugs in the
>> algorithms, but I do have tests for what is currently there (at least
>> for the numeric ones) at <http://hg.gsnedders.com/php-html-5-direct/file/tip/tests/numbersTest
>>> (see the README file in the same folder for more info).
> Thanks for the pointer to test materials; if you can isolate
> any tests where the XSD design would lead to different
> results, I'd be much obliged.

Part of the problem is that XSD datatypes don't have well-defined  
processing requirements against which to write test cases or to  
implement UAs.

"[Definition:]  error
    A violation of the rules of this specification; results are  
undefined. Conforming software ·may· detect and report an error and  
·may· recover from it."

For example, it is defined what an XSD 'decimal' looks like, but  
parsing the value is not defined with well-defined behavior on error.  
HTML 5 specifies how to parse the values (with error recovery that is  
compatible with existing content).

On the validity side, HTML 5 doesn't allow the space characters before  
or after the value but XSD does. Thus, the HTML 5 definitions  
implement both sides of Postel's Law.

Henri Sivonen
Received on Wednesday, 2 April 2008 19:36:20 UTC

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