Another example is the characterization of filters for direct
imaging. For instance, the NOAO Mosaic camera team maintains a list
of filters that includes both a long identifier - unique but hard to
remember - as well as a short identifier, such as "R". Each short
identifier may correspond to several long identifiers, that is, to
several individual filters.
If UCDs were used to create and track such lists, one could attempt
to achieve the same many-to-one mapping by relying on the
hierarchical nature of UCDs:
filter.R.this_is_a_specific_wideband_R_filter. This has problems on
both ends. First, there will often be a redundant prefix like
"filter." and second, who is to say that it is the "R-ness" of the
filter that we wish to capture in a short nickname? Perhaps we
rather need to capture the "wideband-ness" of the filter. The
problem with relying on a hierarchy in a single namespace is
precisely that only one hierarchy exists per namespace. On the other
hand, multiple mappings are trivial with multiple namespaces.
The essential nature of a viable solution will be some mechanism for multiple authorities to maintain multiple non-local lists that permit such niceties as versioning. In the absence of such a mechanism, separate projects will field separate, non-interoperable solutions.
The trouble with anecdotal examples is that they are too easy to gather. The difficulty with this mechanism (whether realized as UCD namespaces or as RDF or as brute-force lists of aliases) will not be encountered when distinguishing between "stars" and "galaxies", but in the more obscure questions of art as referred to by George.
Rob
seaman-at-noao.edu
Received on 2005-12-01Z20:03:22