[css3-fonts] font-variant-numeric

A few comments on the editor's draft:
   http://dev.w3.org/csswg/css3-fonts/#font-variant-numeric-prop

1. Grammar is too loose.

The current spec specifies
  # <numeric-values> = [lining-nums | oldstyle-nums | proportional-nums | tabular-nums
  #                    | diagonal-fractions | stacked-fractions | slashed-zero]+

But some of these pairs are mutually exclusive, and there's no reason any one
keyword should be specified more than once. The grammar should be

  | <numeric-values> = [ lining-nums | oldstyle-nums ] || [ proportional-nums | tabular-nums ]
  |                    || [ diagonal-fractions | stacked-fractions ] || slashed-zero

This makes the following sentence redundant:
   # The values ‘lining-nums’ and ‘oldstyle-nums’ are mutually exclusive,
   # as are ‘proportional-nums’ and ‘tabular-nums’, ‘diagonal-fractions’
   # and ‘stacked-fractions’.
It should therefore be removed.

2. Keyword definitions too terse.

   a) Several of these terms have reasonably-common alternatives, which should
      be added in parentheses so that people looking for this feature can find
      and recognize it easily.

   b) It might be useful to give a little more explanation of what they mean.
      E.g., explain what distinguishes a lining number from an oldstyle number.

~fantasai