Interop with/use of accessibilityFeature property for MathML

I was investigating the question of whether there is a standardized way to annotate the target consumer for a given MathML dialect, mostly thinking of assistive technology.
(short answer: There isn't)

Instead, I discovered that ePub 3 has put in some work to leverage schema.org vocabularies for annotating various features that may or may not be enabled in a given document.

Most relevant may be the accessibilityFeature property, ands its schema.org accessibilityFeature vocabulary.

That effort seems to have independently (or has there been contact?) invented an annotation for chemical formulas, called MathML-chemistry.

The great enabling feature of using this approach is that we can do global, document-level, annotations, which we are currently missing. And it is helpful that it documents a fixed vocabulary for feature flags.

Reading their current vocabulary, this would be an example that the MathML on a page is already remediated for accessibility, either via alttext "or other means" and pertains to chemistry:

<article vocab="https://schema.org/" typeof="DigitalDocument">
   <meta property="accessibilityFeature" content="describedMath"/>
   <meta property="accessibilityFeature" content="MathML"/>
   <meta property="accessibilityFeature" content="MathML-chemistry"/>
   <!-- ... -->

Suggestion: I think the WG should discuss the mechanism and its possible use in MathML 4, and if seen favorably -- suggest helpful extensions.

Start by reviewing the linked schema.org accessibilityFeature vocabulary and the MathML-chemistry entry, then compare the proposed document-level HTML annotations with the current MathML 4 editors draft. The issue is done when the WG has discussed whether to use this mechanism and, if favorable, identified helpful extensions.