New UCDs for VOEvent please

[Frederic V. "Rick" Hessman]

> I'm becoming more skeptical that IVOA standard UCDs are appropriate  
> for representing the often slippery nature of astronomical "processes"  
> and "objects".  The question is whether the characterization of  
> astronomical objects/processes represents "metadata".  The whole point  
> of the precision of a UCD specification (e.g.,  
> phot.flux;em.optical;meas.error;stat.max) is to provide a solid  
> foundation for building a sound scientific argument - but such an  
> argument typically results in drawing new insights and building new  
> logical connections - often using new vocabulary.  On the other hand,  
> even the most well established nomenclature regarding astronomical  
> objects and processes is subject to revision and extension as better  
> data and more profound theory collide.

Ah, but the point of UCDs is not to let computers write papers but to  
be able to let computers organize and re-organize information using  
terms which we can easily formulate/manipulate.  At a pretty trivial  
level, it can be something as simple as saying what the point of an  
observation is/was (the reason why a target classification is needed in  
RTML) or to describe what is roughly happening so that a computer can  
respond to it (the reason it's needed in VOEvent), but a broader use  
within the VO is obvious. While we're all spoiled by the services  
provided by Simbad, resolving astronomical names and querying  
catalogues won't permit us to combine information to the fullest unless  
we can express what it is we have and what we want in a fashion which  
goes far beyond the present IVOA/UCD (crafted really only for VOTable).

Thus, RTML and VOEvent would certainly get by using their own little  
classification lists, but the adoption of a more generally used UCD for  
astronomical objects and processes is bound to become necessary.   The  
earlier we start discussing it, the faster we will be able to profit  
from it.

Fortunately, a supernova will always remain a supernova and a spiral  
galaxy won't loose it's spirals within our lifetime, so the evolution  
of UCD's will be in the direction of the addition of new terms - as  
they become needed - and the passive abandonment of old UCD's which no  
longer serve any but a purely historical purpose -  well, we should let  
historians of science keep their access to old terms (they may actually  
want to know what a W UMa star was/is ;-)

> 	3. Only a single UCD should be appropriate for a given concept.
> 	4. UCDs should be complete, describing all concepts of interest.

Rots of ruck!  A UCD which attempts (!) to describe what it is we do  
will never be complete and unambiguous.  The point is not that it can  
be perfect but that it exists at all.

> However much effort is expended to constrain and mandate standard  
> usage, the users will seek ways to subvert the dominant paradigm.   
> This isn't just the nature of users, it is the nature of science as  
> poetry.  Careful support for alternate usage is the key to controlling  
> anarchy.

Frankly, I imagine that most users won't even see it.   We're doing  
this to help stupid computers become more useful and not to constrain  
the science of our colleagues.

Rick

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Dr. Frederic V. Hessman      Hessman at Astro.physik.Uni-Goettingen.DE
Universitaets-Sternwarte     Tel.  +49-551-39-5052
Geismarlandstr. 11                Fax +49-551-39-5043
37083 Goettingen                 http://www.uni-sw.gwdg.de/~hessman
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MONET: a MOnitoring NEtwork of Telescopes
http://monet.uni-goettingen.de
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