[Om] Questions about representing units

[Christoph LANGE]

On Saturday 21 February 2009 19:34:45 Professor James Davenport wrote:
> On Sat, 21 Feb 2009, Professor James Davenport wrote:
> > > Then, how about compound units?  There are some convenience symbols
> > > like metres_per_second, but what do we need them for?  Wouldn't it make
> > > more sense
> > > to do without them (as you suggested to do without metre_squared) and
> > > write instead: <snip>divide</snip>
> >
> > It probably would do. As and when we can declare individual symbols
> > obsolete, I will propose doing so to MOST of these - memory says there
> > are some odd ones, but i can't remember offhand.
>
> It's come back to me. The ones we DO want are miles_per_hour etc., since
> the abbreviation, mph, is non-standard.

Really?  To my understanding it's wrong to represent such abbreviations on the
OpenMath level.  And, secondly, I find miles_per_hr in the OpenMath CDs, but
I don't find any reference to "mph".  So how did you represent this
abbreviation?

<potential-bias type="omdoc kohlhase ...">
More generally, probably off-topic for this discussion, but nevertheless
interesting (IMHO), a comment on what you said about abbreviations in your MKM
2008 paper:  I wouldn't agree with a representation of abbreviations by
introducing additional OpenMath symbols -- your two "alternative definition"
cases in that paper.  I share your view that "this isn't an OpenMath problem".
You suggested OWL as a solution.  I don't completely agree with that.  OK, one
could introduce a string-valued OWL "datatype property" for annotating
OpenMath unit symbols with their abbreviation, e.g. leading to an annotation
like

http://www.openmath.org/cd/units_imperial1#miles_per_hr
http://www.openmath.org/ns/unit-annotation#abbrev
"mph".

(Recall my OM3 Trac posts about more flexible metadata; within such a
framework, one could even embed this into an OpenMath CD.)

But then, we'd require an application to know OWL, or at least this particular
annotation vocabulary.

More naturally from my point of view is treating this problem as a problem of
rendering OpenMath to presentation markup.  For that, our (admittedly,
not-yet-standard) approach is defining notations, and we do that by mapping
content markup patterns to presentation markup templates.  That said, we could
easily define a "presentation context" "abbreviated" and then map

units_imperial1#mile to "mi"
units_time1#hour to "hr"
(arith1#divide units_imperial1#mile units_time1#hour) to "mph".

… i.e. solve the problem without introducing an additional symbol.
</potential-bias>

What do you think about that?

Cheers,

Christoph

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

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