units symbols

[Carlos Rodrigo Blanco]

Hi

The VOSpec model for treating units has proved to be very 
useful and I think that it could be a very good idea to 
use it in general. At least,I would take it as a good 
starting point and try to improve it if necessary to apply 
it in a more general form.

Carlos Rodrigo

>
> Thanks very much Jesus,
>
> The VOSpec model will be very useful.
>
> Please can I ask anyone with important information or comments, 
> especially references to useful documents, to put them on the wiki page
>
> http://www.ivoa.net/twiki/bin/view/IVOA/UnitsDesc
>
> thanks
>
> Anita
>
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
> -
>
> Dr. A.M.S. Richards, AstroGrid Astronomer, University of Manchester, 
> Jodrell Bank Centre for Astrophysics, Turing Building, University of 
> Manchester, M13 9PL
> +44 (0)161 275 4124
> and
> MERLIN/VLBI National Facility, Jodrell Bank Observatory, Cheshire SK11 
> 9DL, U.K. +44 (0)1477 571321 (tel) 571618 (fax)
>
>
> On Thu, 4 Oct 2007, Jesus Salgado wrote:
>
>> 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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>