units symbols

[Jesus Salgado]

Dear all,

I have been reading the different valuable contributions about the
different standards for units and, more than ever, I think the purpose
of the creation of a work package inside the DM group for unit
description is to define what a unit is. 

I could be wrong but the final output I expect is a data model, not a
recommendation of which standard should be adopted. Of course, as a
consequence of this effort, one existing standard could be recommended
because we would be able to analyze the different existing standards
with more information and to estimate if one of the standards is better
than the other.

As you already know, in VOSpec we already work with a mini-model for
units that could be defined as:

- String representation
- UCD
- Scaleq
- Dimeq

(see http://arxiv.org/pdf/astro-ph/0511616)

The problem is not so simple as, for the conversion of units, a
"conversion object" should be created with no only the initial and final
unit for the conversion, but the numerical value of the magnitude, the
constants that characterize the problem and other magnitudes of the
problem (with their values and units), as all of them could be needed in
the conversion (all of them would be the "dimensions" of the problem).
This is a quite general procedure and, in my opinion, it is a good
starting point to start the abstraction of a units data model.

We will document this approach properly as a contribution to the work
package.

Best Regards,
Jesus
-- 
Jesus J. Salgado


ESAC Science Archive Team
e-mail: Jesus.Salgado at sciops.esa.int
Tel + 34 91 8131271

European Space Agency/European Space Astronomy Centre
VILLAFRANCA Satellites Tracking Station
P.O. Box 78
E-28691 Villanueva de la Cañada
MADRID - SPAIN


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