On Apr 26, 2005, at 3:28 AM, Rick Hessman wrote:
> I've added more VOEvent examples, several suggestions for IVOA/UCD to
> the proposed
> object/event/process UCD list at
>
> http://monet.uni-sw.gwdg.de/twiki/bin/view/VOEvent/
> UnifiedContentDescriptors
Good start at a list. A search facility would add immensely to its usefulness as the list grows. This would also function as a validator for an astronomer's guess as to the proper syntax for a familiar class of objects.
> If something like this list has already been created, I'd appreciate
> hearing about
> it before I put much more work into our own.
This would be a good opportunity for VO to reach out to the larger community. It really isn't for us to mandate nomenclature. An interactive dictionary/beastiary of astronomical objects and processes could be useful all by itself, and will be of obvious utility for various VO projects. A common understanding of each "hypothesis" will indeed be key to VOEvent, for instance.
I'm not sure, however, that the ApJ keywords are the best model for constructing this content descriptor list. Keywords are a way to partition the level of interest a member of the community may have in reading a paper. A UCD is a way of partitioning the underlying physics. For instance, given that the interest in working on this is arising out of VOEvent, it isn't surprising that there is a focus on processes more than objects, and that the selection of objects would be weighted toward time variability in various ways. There are dozens of fine shadings between variable stars. On the other hand, while one can distinguish between elliptical, irregular and spiral galaxies, there isn't any mechanism (yet) for specifying the precise type of each.
I'm leery of encouraging these descriptors to become longer than they are, but it seems inappropriate to specify generally descriptive classes, like:
stars.variable.irregular stars.variable.long_period stars.variable.semi-regular
at the same level as members of prototypical classes, like:
stars.variable.Cepheid stars.variable.RR_Lyr stars.variable.RS_CVn
(And where is stars.variable.W_UMa? Just pointing out that the list will never be complete.)
Perhaps it should be stars.variable.class.Cepheid? Or better yet, adjust in the other direction, maybe stars.variable.period.irregular? Or ideally, a general mechanism might be provided for parametrically classifying periodicity.
The challenge here is not only that the list will never be complete, it is that we should be encouraging researchers to actively augment and improve the list. A workable classification scheme is often the first step in organizing a research program. But the result of a research program is often to overturn the original classification scheme. We don't want to provide a mechanism that is only useful for describing objects far removed from the cutting edge.
Rob Seaman
NOAO
Received on 2005-04-26Z14:20:47