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Re: empty set symbol in MathML

From: Robert Miner <RobertM@dessci.com>
Date: Mon, 5 Apr 2004 09:51:13 -0500
Message-Id: <200404051451.i35EpD022562@wisdom.geomtech.com>
To: info@soft4science.com
Cc: www-math@w3.org


Other experts will correctly me if I'm wrong, but my memory is that
Unicode doesn't acknowledge these as separate character. Instead, they
are regarded a "glyph variants" of the same character, and thus they
do not get separate code points.

This is supported by a quick search of the Unicode 4 character
database.  Another family of characters that are separate in TeX, and
for which we requested separate codepoints are the long arrows.  In
this case also, Unicode rules they were glyph variants.

Consequently, apart from the inherently fragile <mglyph> construct,
there is no good way to distiguish these characters within MathML.


> In the MathML 2.0 spec the entities: &empty; and &emptyv; are mapped 
> to the same unicode number 2205, but these are different symbols in LaTeX.
> empty,                     U02205, /emptyset - zero, slash, [EMPTY SET]
> emptyv,                    U02205, /varnothing - circle, slash, [EMPTY SET]
> Rendering in LaTEX:
>   /emptyset  =  zero, slash,
>   /varnothing  = circle, slash
> MathPlayer 2.0 renders U02205 (empty and emptyv) as slahed circle, while Mozilla renders U02205  as slahed zero.
> Is the entity &empty; mapped to the wrong unicode? 

Dr. Robert Miner                                RobertM@dessci.com
MathML 2.0 Specification Co-editor                    651-223-2883
Design Science, Inc.   "How Science Communicates"   www.dessci.com
Received on Monday, 5 April 2004 10:51:48 UTC

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