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Henri in bug In bug 9965, regarding CDATA and non-CDATA attributes: Comment #12 From Henri Sivonen 2010-06-22 07:17:09 ------- With <!DOCTYPE html>, all attribute are CDATA attributes. However, if you use one of the permitted XHTML 1.0 doctypes and the XML processor processes external entities, some attributes aren't CDATA attributes. As for it being an issue, the document tree would be *different* which implies not polyglot. ---------------- So, there should be 4 options: 1) Say that the DOM differences are acceptable 2) Variant of 1): Say that polyglot spec is only meant for HTML parsers and XML processor without external entity handling 3) Declare XHML1.x doctypes as incompatible with polyglot spec. 4) Require such strict authoring requirements that document is treated the same way, regardless of DTD/DOCTYPE In case of 3) then that also decides what kind of DTD based doctypes that could be permitted: Only those that do not declare anything _but_ CDATA attributes. This is a judgement call: even when it comes to CDATA attributes, then there are differences - namely: HTML parsers do not perform any XML-like normalization. So, it would be possible to say that even CDATA attributes cannot become similar enough.
If I read things correctly, most of these doctypes will cause such entities to be supported in conforming XHTML5 implementations: http://dev.w3.org/html5/spec/Overview.html#parsing-xhtml-documents Older implementations and other XML parsers could have issues, but the polyglot spec is focusing on HTML5 implementations--at least for now. If time and resources allow, perhaps notes for earlier implementations could be added later (if necessary). Thanks so much for the feedback!