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UCDs Notes on discussion 2003 October 16 14:00 – 16:00.

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Presentation on theme: "UCDs Notes on discussion 2003 October 16 14:00 – 16:00."— Presentation transcript:

1 UCDs Notes on discussion 2003 October 16 14:00 – 16:00

2 Roy Williams and Sébastien Derriere Introduction Need for revision of current UCD scheme Presented UCD working draft V1.9.9 General form: : ; Examples: –;phot.flux; –;src

3 Wide-ranging discussion How to support covariance, e.g. proper motion and declination? Where is boundary between UCDs and Data Models? Ideally need normalised vocabulary, but IAU Thesaurus is 10 years out-of-date. What happens to UCD if columns are combined, e.g. arith.sum ?

4 Patricio Ortiz Presented analysis of most popular UCDs showing the complexity of the problem. This was followed by a further inconclusive discussion. Some topics raised: –How/whether to support grouping – generally felt to be responsibility of data model: UCD should be applied to a column as an entity. –Is equinox needed as attributed to positional coordinates? –Can UCDs be applied to parameters as well as columns?

5 Tom McGlynn Proposed somewhat simplified scheme for UCD2 –Fewer top-level items, mainly physical concepts such as position or flux. –To be followed by one or more attributes/qualifiers Waveband, measurement type, etc. Value (this one alone may be omitted as the default) Error, max, min, etc.

6 Straw vote taken Do we need new UCDs, or keep old ones –In favour of existing UCDs: ~4 –In favour of some form of new UCDs: ~25 –There were also a few abstentions.

7 Demonstration of Aladin by Pierre Fernique Showed Aladin using UCDs to limit the number of stars plotted on an image –Select [PHOT*] < 16 Can also be done in UCD-2, perhaps even more effectively.

8 Conclusions A move to some form of UCD-2 was generally supported. The simplification and rationalisation proposed by Tom McGlynn attracted relatively few criticisms and several favourable comments. Coordination is desirable on the appendix to UCD-1.9.9 which has a table of waveband names, e.g. em.UV.200-300nm –These should be aligned with the waveband names or classifications proposed by the Registry and Data Model groups.

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