lspace/rspace have confusing names

[bert-github]

(This is part of the I18n WG review.)

3.2.4 Operator, Fence, Separator or Accent
https://www.w3.org/TR/mathml-core/#operator-fence-separator-or-accent-mo

From the algorithm in 3.3.1.2 Layout of <mrow> it follows that the lspace and rspace attributes of an element add space before, respectively after the element. In a right-to-left formula, that means lspace is on the right and rspace on the left. The names suggest otherwise and when the attributes were created, some 28 years ago, they actually did mean left and right.

To avoid confusion, maybe the spec should explicitly say, in a note, that ‘l’ does not mean ‘left’. (There is an image, figure 10 that contains the words ‘leading’ and ‘trailing’, but doesn't explicitly link them to lspace and rspace.)

[dginev]

"leading" and "rear" could be a good pair of words to map to the l/r letters.

[davidcarlisle]

Leading and tRailing are how these are described in mathml 3 and 4, I don't think we should try to introduce "rear" at this stage. But I'd agree with adding a note, the interpretation of these attributes in an RTL context is currently clearer in mathml full which says

Specifies the leading space appearing before the operator; see 3.2.5.6.4 Spacing around an operator. (Note that before is on the right in a RTL context; see 3.1.5 Directionality.

[bkardell]

I agree we could add clarity here - tbh I personally even find it confusing that there is not a link that really defines them exactly - in any case, @davidcarlisle can you add such a note?