Re: Super and Subscripts

Bert Bos (
Mon, 16 Jan 95 10:52:05 EST

|I think we ought to be saying that <sup> and <sub> can be used on their
|own for isolated single expressions with no operators, but that if you
|want operators, you have to say <math>X<sup>n</sup> + Y<sup>n</sup> =
|Z<sup>n</sup></math> (with omissible spacing, like TeX) so that the
|display engine can make sense of the formatting. Otherwise we'll only
|get a storm of complaints.

<SUB> and <SUP> can be used on their own in running text (I don't know
what they are useful for, but anyway). But in a formula, I would like
to see less ambiguous markup. Consider:

E=c m <MATH>E=c<SUP>2</SUP>m</MATH>

Does the `2' belong to the `c' or to the `m'?

Ideal would be a syntax that is easy to format, yet still allowed
unambigous translation for input to an equation solver. It may require
that the author insert `invisible parentheses' like <BOX></BOX> to
make the meaning clear. Wasn't Phil Hallam-Baker working on such a

There are several solutions:

1. Use different tags for different meanings (<POWER>, <ATOM>)
2. Use the same tag (<SUP>), but with a ROLE attribute
3. Attach a role attribute to the formula as a whole ("MATH", "CHEM")


                          Bert Bos                      Alfa-informatica
                 <>           Rijksuniversiteit Groningen
    <>     Postbus 716, NL-9700 AS GRONINGEN