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Re: Schemas and validation

From: Joe D Williams <joedwil@earthlink.net>
Date: Mon, 1 Mar 2010 15:10:12 -0800
Message-ID: <AD6A3CE846284E8898775EA03A560E98@joe1446a4150a8>
To: "Maciej Stachowiak" <mjs@apple.com>
Cc: "Henri Sivonen" <hsivonen@iki.fi>, "Leonard Rosenthol" <lrosenth@adobe.com>, "Anne van Kesteren" <annevk@opera.com>, "Larry Masinter" <LMM@acm.org>, "'Toby Inkster'" <tai@g5n.co.uk>, "'Adam Barth'" <w3c@adambarth.com>, "'HTML WG'" <public-html@w3.org>
Maciej Sent: Monday, March 01, 2010 12:22 PM
> On Mar 1, 2010, at 11:57 AM, Joe D Williams wrote:
>
>>> no schema language can capture all the conformance requirements of 
>>> XHTML5.
>>
>> maybe so, because some requirements are runtime.
>
> Henri's not talking about runtime requirements. The static machine- 
> checkable syntax conformance requirements of HTML5 cannot be fully 
> and  correctly expressed in any of the existing popular schema 
> languages.

OK, like the URI example?

>
>> If we can't produce a valid (highly informative) XML Schema that 
>> can  accurately represent the authortime syntax and sctructure 
>> requirements, then there will be no firm standards-track crosscheck 
>> between authortime content structures, the intent of the standard, 
>> and the runtime of the operating browser.
>
> The crosscheck would be to use the validator.

Aren't we seeing some success with schema-driven validators?
With content exceptions present in html5 I could expect that some 
hand-tooling would be required to accept all html5 code, but I also 
would believe it should be possible to construct a schema that could 
valdate a target "correct' or recommendied form that could tell us if 
elements are not structured as intended by the spec, and some other 
details.

> If you want a schema  that approximates most of the requirements, 
> validator.nu includes a  RelaxNG schema that anyone could use for 
> their own purposes. But it  should not be assumed that any content 
> satisfying this schema is  correct.

I think I understand the the limits of content correctness in 
validation, but the schema just tells about elements and attributes 
and acceptable structures and maybe values, froms, ranges. Maybe my 
experience, or what I think I am getting  is wrong. I believe that the 
browser could run something just fine that would not pass validation, 
but if valid, it should at least run.

>
> My understanding is that DTDs and XML Schema are both significantly 
> weaker than Relax NG and can represent even fewer of the 
> requirements  accurately.

DTD for sure no way, I think. I am looking for a schema example. What 
element/attribute structures, attribute values, and content element 
features in html5 can't be shown via xml schema. The ones I might be 
able to name I hope are fixup cases where maybe something in the user 
code has been left out and gets 'fixed' in some way by the browser. 
Schema validation should fail that until fixed. Or, things that are 
obsoleted but ok, and maybe others like that where the html5 UA makes 
up for missing information. But I do not see main structural stuff in 
html5 that seems out of line. So, I would still be looking for an 
example of what parts/structures/content of html5 can't be modelled 
with the mostly standard XML schema?

Sam > Second, I suggest that people who wish to discuss this topic 
(yet
again!) do so in the context of bug 8611:

http://www.w3.org/Bugs/Public/show_bug.cgi?id=8611

Yes, for html it should cover only the recommended html constructions 
(no fixups and few if any execeptions allowed) and all valid xhtml 
constructions should be documented.


Thanks and Best Regards,
Joe
Received on Monday, 1 March 2010 23:11:36 UTC

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