[Units]

[Francois Ochsenbein]

Hi Anita, Rob, Bob, Christophe,

I share your concern -- and surely no, the Unit document should
almost never be updated. If we assume that the FITS is the core
(which I think should be reviewed carefully, because it accepts
several ways for operators), then no individual protocol would
be allowed to recommend a unit named e.g. 'cc' meaning 'cm3'. 
It's exactly point 1A of Rob's message -- define what's not
conforming.

The necessity of subsets results from existing protocols -- cone
search specifes the output of the position is in degrees for 
instance...

Cheers, francois

>
>
>Hi Mireille,
>
>Sorry I missed the discussion.  Also, I do not know what is hard or easy
>for all the developers actually doin g the hard work with code.  But I
>would have thought that, for the units where conversions are simple
>(linear, powers of 10, etc.) there is no point in being restrictive for
>the sake of it.
>
>I am talking about what units we _recognise_; for internal use, we
>either pass them through undigested as per original, or we use a
>common system - I hope thta SI won...
>
>I do not know why people want different subsets of units for different
>protocols but I would have thought that leads to confusion and to
>standards not being interoperable (which is sabotaging the requirement
>from data providers and astronomers e.g. to be able to get a suite of
>images, spectra, tabulated data etc. for a given region of interest,
>etc.).
>
>So I am very alarmed by the suggestion below, but maybe someone can
>reassure me.
>
>thanks
>a
>
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
>Dr. A.M.S. Richards, UK ARC Node/AstroGrid,
>Jodrell Bank Centre for Astrophysics, Alan 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)
>
>"Socialism or barbarism?" Rosa Luxemburg (1915)
>
>On Thu, 28 May 2009 louys at alinda.u-strasbg.fr wrote:
>
>> Hi all,
>> In the DM1 session, we had a discussion (too short) about Units, following
>> the suggestion made by A. Micol on these same lists.
>> The questions are :
>> 1)should the IVOA protocols allow only a subset of the IVOA supported Units
>> expressions ?
>> If yes , who would volunteer to list up the wished units for each protocol?
>> SIAv1,
>> SIAv2
>> SSA
>> SimDAP
>> SLAP
>> others?
>>
>> 2) should these supported units sets published in protocols documents or in
>> the Units draft?
>>
>> thanks for your comments / suggestions .
>> Mireille, DM chair
>>
>>
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Francois Ochsenbein    ------   Observatoire Astronomique de Strasbourg
   11, rue de l'Universite 67000 STRASBOURG  Phone: +33-(0)390 24 24 29
Email: francois at astro.u-strasbg.fr (France)    Fax: +33-(0)390 24 24 17
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