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Re: Write-up about semantics in HTML5 from A List Apart

From: Julian Reschke <julian.reschke@gmx.de>
Date: Wed, 07 Jan 2009 13:43:52 +0100
Message-ID: <4964A388.20206@gmx.de>
To: Ian Hickson <ian@hixie.ch>
CC: John Allsopp <john@westciv.com>, public-html@w3.org

Ian Hickson wrote:
>> I'd prefer extensibility also to address future problem (at least to try 
>> that), otherwise it's really a poor kind extensibility :-)
> We can't possibly design an extension mechanism to address use cases, 
> requirements, and problems that we know nothing about.

Well, I disagree.

It works just fine in other areas.

>> That is misleading. The important difference in XML is that the syntax 
>> is frozen (-> no new parser required, at least in theory (*)), but 
>> XML-based languages are extensible nevertheless (on the vocabulary 
>> level, not the syntax level).
> This is exactly what we have with HTML5. There are half a dozen or more 
> extension mechanisms in HTML5, allowing you to extend all kinds of aspects 
> of the language in ways that resolve problems we know about today. One of 
> the things you cannot do, as with XML, is extend the syntax without 
> changing the language.
> (There are a number of things that XML can't do because of its limitations 
> in extensibility. For example, authors can't extend it to represent 
> non-tree structures, they can't extend it to have error recovery, they 
> can't extend it it to have true multivalued-attributes, they can't extend 
> it to allow them to correctly define validity in the face of namespaces, 
> and they can't extend it to allow them to define validity for 
> non-enumerated attribute values. This isn't a criticism of XML, it's just 
> a description of the design choices made by the XML working group. It's 
> normal for a language to have a constrained extensibility model.)

All true.

But in XML based languages you can extend the vocabulary, and this you 
can't in HTML. At least not the way it's currently defined.

BR, Julian
Received on Wednesday, 7 January 2009 12:44:36 UTC

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