On Jun 1, 2005, at 10:25 AM, Sebastien Derriere wrote:
> <src>
> <param ucd="meta.id" value="NGC12345" />
> <param ucd="src.class" value="Galaxy" />
> <param ucd="src.morph.type" value="Sc" />
> </src>
This is similar to how I was envisioning VOEvent usage. Rick should speak up (on whatever mailing list :-) if he sees this much differently. That said, I question whether these specific UCDs will survive our discussions.
> instead of saying: "This object is a spiral galaxy", I'd rather say
> "The result of the classification process gives for this object the
> value [galaxy] for the source class, and the value [spiral] for the
> morphological type".
I think we need support for both. A name is sometimes both an enumerated value and a hierarchical classification. This is particularly true when the words express some underlying physics (or merely physical description) that is still plastic. We think we have a pretty good idea now what a "spiral galaxy" is. It wasn't so very long ago that we hadn't the slightest idea of its true nature. As long as astronomy is a living subject, there will be names with fluid meanings.
Another concern is that a "src.class" expression would cover vast expanses of phase space - dozens of orders of magnitude in size (from chunks of rock in the solar system to cosmological structure) and having to distinguish between objects and processes with every possible physical/chemical/even biological property in play. Imagine a UCD-like expression of some field of biology - human anatomy, for instance. The corresponding sci.class would only have to distinguish a modest size range and modest variety of entities. (There are something like 200 cell types in the body.) What we're looking for is a reasonable way to separate the equivalent of cell biology from tissue biology from physiology at the level of organs.
In particular, the allowed values for different UCDs become interrelated. (This seems likely to be something you folks have previously considered.) There are different values for src.morph.type depending on the value of src.class - and there are even different sets of UCDs entirely that are pertinent depending on the class.
In short, Sebastien's view and Rick's view need to be synthesized into a common vision.
> If we start creating words for each "concept" that we can name, we
> go the wrong direction.I'd create a UCD word for objects
> in the constellation Draco,
But this is precisely what is done all the time. An astronomer pursues a new line of research and invents new terminology. Those terms may be representative of universal phenomena or may be specific to some area of study. We're hundreds of years past caring about constellations scientifically, but the details of some specific galaxy or cluster (M13, the Hyades) may be very important to describe accurately and precisely. To borrow a page from Rick, if UCDs don't support project specific glossaries, these will be expressed in some other fashion.
Rob Seaman
NOAO
Received on 2005-06-01Z20:04:13