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Bug 20198 - Formally define that polyglot can be extended
Summary: Formally define that polyglot can be extended
Alias: None
Product: HTML WG
Classification: Unclassified
Component: HTML/XHTML Compatibility Authoring Guide (ed: Eliot Graff) (show other bugs)
Version: unspecified
Hardware: PC All
: P2 normal
Target Milestone: ---
Assignee: Leif Halvard Silli
QA Contact: HTML WG Bugzilla archive list
Depends on:
Blocks: 12725 20201
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Reported: 2012-12-03 05:36 UTC by Leif Halvard Silli
Modified: 2013-04-24 01:32 UTC (History)
5 users (show)

See Also:


Description Leif Halvard Silli 2012-12-03 05:36:31 UTC

Issue: the XML/HTML task force came to the, in my view, incorrect conclusion that polyglot markup cannot be extended. 

On the question "2.4 How can islands of XML be embedded in HTML?", the group concluded that polyglot markup, for pure validation reasons, was no aid:

"Note also that polyglot markup is not an aid here as it forbids arbitrary XML content from the document."


But this conclusion, which sounds like thinking from the era of DTD-based XHTML, seems just as correct and as it is gravely wrong.

Because the thing is that HTML5 itself cannot be extended. Or, it can be extended. But then it is not HTML5 anymore. (Though - ah - there is a difference, when I think about it, between being extended via applicable spec and be extended by some extra spec.)

So, perhaps say something like this - as an informative note somewhere: 

Polyglot markup, itself being HTML5, supports extensiblity according to the rules that HTML5 draws up <>,  but the extension must pay attention to fullfilling the polyglot principles. Also, it should probably be said that that polyglot markup stops being polyglot markup, in the formal sense, in the moment the markup stops conforming to HTML5. (If there are some extension methods that shoud definitely be ruled out as not polyglot, then of course it would be fine to mention it.) And, also - being XHTML5, it could - on a postive note - be fine to say that polyglot markup can be easily extended when or if it is served as applixation/xhtml+xml.
Comment 1 Eliot Graff 2013-04-24 01:32:02 UTC
Added this to the (informative) Introduction:

Polyglot markup, itself being valid HTML5, supports extensibility as it is defined in Section 2.2.3 Extensibility of HTML5, so long as the extension does not violate the rules of polyglot markup. [HTML5] In addition, being well formed XML, polyglot markup can be extended when it is served as application/xhtml+xml. 

new revision: 1.100; previous revision: 1.99