[Om] invisible times and invisible plus

[Christoph LANGE]

Dear Jan Willem,

2009-08-31 14:23 Jan Willem Knopper <jknopper at win.tue.nl>:
> Is there a way to describe in OpenMath that a certain times or plus
> symbol is invisible ?

AFAIK there is no standard way, and IMHO there should not be a standard way.
I think there are two nonstandard solutions, one of which should be chosen as
appropriate for the particular application:

1. define a special OpenMath symbol not just for the "invisible plus" in a
   mixed fraction, but a specific constructor for the mixed fraction.
   (Compare James' favorite landau-in example, where he also introduces a
   completely new symbol.)
2. use the normal plus, but annotate the whole expression with some
   information that causes the renderer to render the plus invisibly.

1. could look like

<OMA>
  <OMS cd="my" name="mixed"/>
  <OMV name="whole"/>
  <OMV name="num"/>
  <OMV name="dem"/>
</OMA>

2. could look like

<OMATTR>
  <OMATP>
    <OMS cd="my" name="preferred-presentation"/>
    <OMS cd="my" name="mixed-number"/>
  </OMATP>
  <OMA>
    <OMS cd="arith1" name="plus"/>
    <OMV name="whole"/>
    <OMA>
      <OMS cd="arith1" name="divide"/>
      <OMV name="num"/>
      <OMV name="dem"/>
    </OMA>
  </OMA>
</OMATTR>

I could imagine a more sophisticated attribution with the context-related
stuff developed by my colleagues, see Kohlhase/Müller/Rabe MKM 2008.

Cheers,

Christoph

-- 
Christoph Lange, Jacobs Univ. Bremen, http://kwarc.info/clange, Skype duke4701
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