How to handle the remaining MathML BCD keys

[captainbrosset]

We already have a MathML feature on the repo: https://github.com/web-platform-dx/web-features/blob/main/features/mathml.yml which contains quite a lot of BCD keys.

Looking at the list of remaining unmapped BCD keys, I see there are quite a few still. These are marked as deprecated on BCD.

How do we want to handle them on this repo?

• maction - Entire element is deprecated

  • mathml.elements.maction
  • mathml.elements.maction.actiontype
  • mathml.elements.maction.actiontype.toggle
  • mathml.elements.maction.selection

• mfenced - Entire element is deprecated

  • mathml.elements.mfenced

• mfrac:

  • mathml.elements.mfrac.denomalign - Deprecated attribute
  • mathml.elements.mfrac.numalign - Deprecated attribute
  • mathml.elements.mfrac.linethickness.named_spaces - Deprecated attribute value
  • mathml.elements.mfrac.linethickness.nonzero_unitless_values - Deprecated attribute value
  • mathml.elements.mfrac.linethickness.thin_medium_thick - Deprecated attribute value
  • mathml.elements.mfrac.numalign - Deprecated attribute

• mmultiscripts

  • mathml.elements.mmultiscripts.subscriptshift - Deprecated attribute
  • mathml.elements.mmultiscripts.superscriptshift - Deprecated attribute

• mo

  • mathml.elements.mo.named_spaces - Deprecated attribute value
  • mathml.elements.mo.nonzero_unitless_values - Deprecated attribute value

• mpadded

  • mathml.elements.mpadded.named_spaces - Deprecated attribute value
  • mathml.elements.mpadded.nonzero_unitless_values - Deprecated attribute value
  • mathml.elements.mpadded.pseudo_units - Deprecated attribute value
  • mathml.elements.mpadded.scale_factor - Deprecated attribute value

• mspace

  • mathml.elements.mspace.named_spaces - Deprecated attribute value

• mstyle - Entire element is deprecated?

  • mathml.elements.mstyle.background
  • mathml.elements.mstyle.color
  • mathml.elements.mstyle.fontsize
  • mathml.elements.mstyle.fontstyle
  • mathml.elements.mstyle.fontweight

• msub

  • mathml.elements.msub.subscriptshift - Deprecated attribute

• msubsup

  • mathml.elements.msubsup.subscriptshift - Deprecated attribute
  • mathml.elements.msubsup.superscriptshift - Deprecated attribute

• msup

  • mathml.elements.msup.superscriptshift - Deprecated attribute

• mtable

  • mathml.elements.mtable.width.named_spaces - Deprecated attribute value

• semantics

  • mathml.elements.semantics.advanced_visible_child_selection - ???

• Global attributes - Deprecated attributes and attribute values

  • mathml.global_attributes.mathbackground
  • mathml.global_attributes.mathcolor
  • mathml.global_attributes.mathsize
  • mathml.global_attributes.mathsize.named_spaces
  • mathml.global_attributes.mathsize.nonzero_unitless_values
  • mathml.global_attributes.mathsize.small_normal_big

[jamesnw]

This is very similar to #2485, where we documented the deprecated SVG keys. Currently, SVG is a "junk drawer", so we opted to make a single junk drawer of discouraged SVG features. My thought is to make a single discouraged MathML junk drawer to match what we did there, and to not have more discouraged MathML features than non-discouraged MathML features.

[ddbeck]

I agree with, @jamesnw. We can reserve the option to split up the features in the future. But until we can demonstrate there's an audience for those features (in contemporary or historic MathML), I think we shouldn't split them up.

If I were making the MathML discouraged feature, I'd probably do a similar thing as SVG:

name: MathML 3 (discouraged)
description: MathML 3.0 specifies several components that were excluded from MathML core, such as the `<maction>` and `<mfenced> elements.