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The HTML+RDFa spec says: ]] If an author is editing an HTML fragment and is unsure of the final encapsulating MIME type for their markup, it is suggested that the author specify both lang and xml:lang [[ NIT: "If an author is [snip] for their markup". Correct: "If an author is [snip] for his/her markup". ISSUE: The advice proliferate the belief that XML mime types *need* xml:lang. But it is only if they don't understand XHTML that they *need* xml:lang. They might very well not understand XHTML. But is that related to the MIME type? The only use case I have heard for xml:lang is XML authoring tools - thus, not exactly "the final encapsulating MIME type". XML parsers of the Web browser kind (IE/Webkit/Opera/Gecko) do understand the @lang attribute. (Though there might be legacy versions which don't.) And e.g. the XHTML+RDFa DOCTYPE supports both @lang and @xml:lang. Are there any *real* reasons for using both attributes - unrelated to authors' fears and feelings? Such as legacy RDFa parsers? Or specific XML authoring tools? Or specific consumers?
EDITOR'S RESPONSE: This is an Editor's Response to your comment. If you are satisfied with this response, please change the state of this bug to CLOSED. If you have additional information and would like the editor to reconsider, please reopen this bug. If you would like to escalate the issue to the full HTML Working Group, please add the TrackerRequest keyword to this bug, and suggest title and text for the tracker issue; or you may create a tracker issue yourself, if you are able to do so. For more details, see this document: http://dev.w3.org/html5/decision-policy/decision-policy.html Status: Fixed/Answered Change Description: Fixed the nit you had (s/their/his\her/) Rationale: The nit submitted was correct. > They might very well not understand XHTML. > But is that related to the MIME type? No, it doesn't have to always be related to MIME type. RDFa processors often put themselves into XML or non-XML mode when processing, one of the ways that they can do this is based on MIME type. In non-XML mode, they shouldn't pay attention to xml:lang. So, if an author marks up their snippet using "xml:lang" and that snippet shows up in an HTML5 document processed in non-XML mode, then the "xml:lang" value would be ignored. This is why we tell authors to specify both.