Hi again
I agree entirely that UCDs should be used to describe what a value represents rather than how it relates to other things. I think that combining UCDs with data models will give us everything we need.
English/typos:
Could we use 'phrase' instead of 'words' since really 'phys.temp' consists of two words 'phys' and 'temp' assembled together?
Sec 3.3 two cases of "applies a magnitude" I think should read "applies to a magnitude"?
Most of these are requests for explanation rather than a request for change:
An astronomical question: given UCDs are not supposed to describe units, why do we still have UCDS like 'phot.mag'? Should this be 'phys.brightness', where the units are magnitudes or janskies or ergs or whatever?
How are words assembled - eg, why pos.eq.ra instead of pos.ra? How will they be extended?
We need more detail on how the UCDs are built up. Using the example of instrument temperature maximum: why is the 'stat.max' added at the end, instead of say, 'phys.temp;stat.max;instr'. Indeed if 'stat.max' is secondary, shouldn't the error be 'phys.temp;stat.error' and we add a 'stat.value' word? Or should we say that order does not matter? If order *is* important this could all get rather fraught.
What is the conceptual difference between a word and a phrase? ie, why phys.temp;stat.max;instr instead of 'instr.temp.max', the latter being built from UCD words 'instr' 'temp' and 'max'?
Requests for change:
Personally I would rather see full names used instead of abbreviations (eg 'physical' instead of 'phys', 'position' instead of 'pos') for anything other than really common terms (ra, dec, max, min). Abbreviations make an insignificant difference to software performance, and can cause confusion especially when non-astronomers are involved in development.
Cheers,
Martin
Sebastien Derriere wrote:
> Hello,
>
> I have placed on the IVOA wiki a PDF version of the latest document
> on UCD: http://www.ivoa.net/internal/IVOA/IvoaUCD/WD-UCD-20040426.pdf
> This document describes the motivations and procedure to evolve
> the first generation of UCD into a new scheme called UCD1+.
> The new scheme has been quite successfully tested on VizieR. It also
> includes inputs from other fields, like the latest SIAP discussions.
> As the UCD1+ vocabulary is likely to evolve faster than the reference
> document itself, the reference lists are available online, together with
> old
> versions and history of changes:
> http://vizier.u-strasbg.fr/UCD/lists/
>
> The document currently has a Working Draft status, but the idea is
> to promote it to an IVOA Proposed Recommendation. This can be done
> once agreement is reached within the discussion group, if I understand
> well the IVOA document lifecycle.
> So... time for discussion now !
>
> Sebastien.
-- Martin Hill Software Engineer AstroGrid @ ROE Tel: +44 7901 55 24 66 www.astrogrid.orgReceived on 2004-04-28Z08:48:57