[whatwg] External document subset support

Henri Sivonen hsivonen at iki.fi
Mon May 18 01:05:56 PDT 2009

On May 18, 2009, at 09:36, Brett Zamir wrote:

> Section 10.1, "Writing XHTML documents" observes: "According to the  
> XML specification, XML processors are not guaranteed to process the  
> external DTD subset referenced in the DOCTYPE."
> While this is true, since no doubt the majority of web browsers are  
> already able to process external stylesheets or scripts, might the  
> very useful feature of external entity files, be employed by XHTML 5  
> as a stricter subset of XML (similar to how XML Namespaces re- 
> annexed the colon character) in order to allow this useful feature  
> to work for XHTML (to have access to HTML entities or other useful  
> entities for one, as well as enable a poor man's localization, etc.)?

See http://hsivonen.iki.fi/no-dtd/ explains why DTDs don't work for  
the Web in the general case.

Loading same-origin DTDs for the purpose of localization is a semi- 
defensible case, but it's a lot of complexity for a use case that is  
way on the wrong side of 80/20 on the Web scale. Besides, if the use  
case for DTDs is localization within an origin, the server can perform  
the XML parse and reserialize into DTDless XML. (That's how I've  
implemented this pattern in the past without client-side support.)

Henri Sivonen
hsivonen at iki.fi

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