Vocab format

[Doug Tody]

On Fri, 14 Sep 2007, Tony Linde wrote:
> No, broader and narrower are relationships: so you would record
> the relationship that SeyfertGalaxy is a narrowing of the term,
> Galaxy. Certainly we would want to record both terms, but do we want
> to record the realtionships? And, to start with, I'd say no. The

Although I normally argue for keeping it simple to start with, I don't
think I agree with this.  Yes, broader and narrower are relationships
(as is hierarchy), and we already see this in the proposed SV and in
other things like UCDs.  The thing is, when we classify a particular
object we would like to be as precise as possible.  But when we
search for objects as candidates for analysis we would often like
to be able to express a broader category which includes all the
subcategories, and refine it iteratively based upon the results
of a search.  Hence for any useful astronomical vocabulary it is
necessary to express relationships and be able to map one to many,
to several levels of detail.

Hence if we know the type of a galaxy we would like to record that as
precisely as we can in metadata such as Target.Class.  But when we
search for data for analysis we might be interested in all "Galaxy"
type objects.  If this is what is meant by broader/narrower type 
relationships, then it is a requirement for this to be useful.

	- Doug