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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."
http://www.w3.org/TR/xmlschema-2/

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
hsivonen@iki.fi
http://hsivonen.iki.fi/
Received on Wednesday, 2 April 2008 19:36:20 GMT

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