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Re: content for characters

From: Robert Miner <RobertM@dessci.com>
Date: Wed, 20 Jun 2001 15:09:38 -0500
Message-Id: <200106202009.PAA22795@wisdom.geomtech.com>
To: dreamthnk@hotmail.com
CC: www-math@w3.org

Hi.

> i was just wondering if there was a way to apply certain characters, for 
> example "plusminus" or "plusmn" as content mathml as opposed to leaving it 
> as presentation mathml since the symbol is not just a constant, but rather 
> represents an operation.

This is kind of a tricky case.  The plusminus symbol is usually really
used as a shorthand for  two separate operators.  One could try to
define a plusminus operator that maps from RxR -> RxR, so that


  3 plusminus 5 = (8, -2)

or something like that, but then you have problems extending all your
other operators to work on lists, e.g what does (3 plusminus 5) * 2
mean?  The * isn't ordinary multiplication anymore, since the operand
on the left is now an ordered pair.

For content encoding, probably the better way to go is to use the
logic contructs, or possible the list construct to write down both the
result of adding and subtracting the arguments.  Thus, the presentation
MathML

<mrow><mn>3</mn><mo>&plusmn;</mo><mn>5</mn></mrow>

best corresponds to a content encoding like

<list>
  <apply><plus/><cn>3</cn><cn>5</cn></apply>
  <apply><minus/><cn>3</cn><cn>5</cn></apply>
</list>

or maybe

<apply>
  <or/>
  <apply><plus/><cn>3</cn><cn>5</cn></apply>
  <apply><minus/><cn>3</cn><cn>5</cn></apply>
</apply>

depending on the context.

--Robert

------------------------------------------------------------------
Robert Miner                                    RobertM@dessci.com
MathML 2.0 Specification Co-editor                    651-223-2883
Design Science, Inc.   "How Science Communicates"   www.dessci.com
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Received on Wednesday, 20 June 2001 16:09:48 GMT

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