Mathml validation - global attributes not recognized.

[daute]

When using https://validator.w3.org/ to validate MathML - by setting the document type to Mathml 2.0 - the example from

https://www.w3.org/TR/mathml-core/#attributes-common-to-html-and-mathml-elements

does not validate; the attribute "dir" is not recognized: there is no attribute "dir"

And I think, one should be allowed to enter data-* tags too (e.g <math data-test="test" dir="rtl"> but they is also not recognized.