Re: units symbols

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


================================================================================================
This message and any attachments are intended for the use of the addressee or addressees only. The
unauthorised disclosure, use, dissemination or copying (either in whole or in part) of its content
is prohibited. If you received this message in error, please delete it from your system and notify
the sender. E-mails can be altered and their integrity cannot be guaranteed. ESA shall not be liable
for any e-mail if modified.
=================================================================================================