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http://html-differences.whatwg.org/#new-elements [[ WHATWG HTML has data which allows content to be annotated with a machine-readable value. ]] 5.1 also has it http://www.w3.org/html/wg/drafts/html/master/text-level-semantics.html#the-data-element
https://github.com/whatwg/html-differences/commit/cfe1a32dce88cd8994e252063949d47e83e943e5