Schemas and validation

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.

> 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. 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.

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

Regards,
Maciej