L2/00-239

Mark Davis <markdavis@ispchannel.com> on 07/07/2000 09:30:45 AM

Please respond to unicore@unicode.org

Subject:  UTC Agenda item: Mathematical Letter Symbols


There are two topics that we need to cover at the next meeting having
to do with the Mathematical Letter Symbols

1. Do we recommend the use of these characters in rich-text
environments: in environments like MathML that have rich enough
structure to encode the proper information (and more, of course)?

2. Do we categorize these characters as Letters or as Symbols?

Here are my thoughts on them.

1. Markup.

Fundamentally, once the characters are encoded in Unicode 3.1, and are
used in accordance with their plaintext semantics, their use is
conformant even in environments where they would be better replaced by
markup or other out-of-band information. So in some sense, the only
thing the UTC can do is make a recommendation. However, we should try
to give guidance on the use of these characters and their interaction
with markup. Since mathematics (except for fragments) has
fundamentally a non-linear structure, thus requiring markup or
equivalent for correct representation, and since mathematics is
fundamentally generative (with some inventive mathematicians somewhere
using some interesting glyphs to convey some distinction), I think our
recommendation should be to replace the clones with markup in
interchange.

2. Symbols
The only basis for adding these characters are that they are NOT
treated as letters -- that they are treated as symbols. Categorizing
them as Sm -- mathematical symbols -- will result in more applications
correctly handing them, and distinguishing them from the true letters.

For consistency, we should revisit the few scattered characters in the
BMP that are filling holes in the math characters, as listed in
http://www.unicode.org/unicode/reports/tr24/charts/ScriptChart0.html.

I feel sufficiently strongly about this that if we cannot agree to
change the few scattered characters, that we should go ahead and fill
the holes, mark them all as Sm, and discourage the use of the
scattered ones.

Mark