Re: Public Review Issue Unicode Technical Report #25, "Unicode Support for Mathematics"

From: Asmus Freytag (
Date: Fri Jan 12 2007 - 16:23:34 CST

On 1/12/2007 8:36 AM, Philippe Verdy wrote:
> From: "Jon Hanna" <>
>> Philippe Verdy wrote:
>>> I'm quite surprized at the conclusions given here about
>>> "'discouraging" the use of superscript and subscript characters,
>>> despite there are languages
>>> into which they are
>>> letters distinct from their respective baseline character counterparts.
>> "Despite?" That seems a very good reason for discouraging use of
>> superscript characters for mathematical superscripts.
> This is definitely not what the TR says, which is much more general.
The first sentence in the section you cite introduces the subject as
"superscript and subscript digits and punctuation that can be useful in
mathematics". I maintain that this sets the scope of the discussion
sufficiently to exclude an extension of the guidelines to their use in
transcription of Minnan. The Spanish a and o are also not part of the
specific ranges mentioned in UTR#25, nor are the majority of
superscripted modifier letters for linguistic notation. Your reading
constitutes an over-interpretation.
> It does not discourage their use for mathematical purpose only...
> Note that the context is important because the TR also speaks about documents that mix both normal text and mathematics/physics (and even in the case of scientific formulas, and LaTeX maths documents, there are occurences of plain-text *within* formulas (for example to express conditions like "x is a prime number", or when using descriptive variable names).
And normal text layout rules apply there, none of which we have
documented in the TR as they are not specific to mathematical notation
per se, but constitute embedded text.
> I am not contesting the fact that use of the superscript 2 character must bediscouraged infavor of markup applied on regular number 2 when the notation really represents an exponent, and similar uses in indices. It's just the way this is formulated which will give wrong advices to implementers and to users.
We decided to not call out exponentiation or indexation, because you are
bound to find some raised digits (or raised + and -) that are neither.
If in math mode, use markup no matter what your semantics are for these.
> The truth is that superscript/subscript markup should be used when its semantic is clearly separable from the semantics of the normal text being subscripted/superscripted, who also keeps its own semantic. Regarding the case of superscript in Mannan, its anusvara-like semantic (postnasalisation of vowels) is not separable like this into a consonnant n, and its text boundaries are not changing the standard baseline of characters. This character is in fact not a superscript as suggested by its glyphic appearance, but a plain letter with a distinct semantic.
That's all a nice theory.


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