Unified Content Descriptor Controlled Vocabulary RFC

This document will act as RFC centre for the UCD - Controlled Vocabulary Proposed Recommendation.

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Discussion about any of the comments or responses should be conducted on the UCD mailing list, ucd@ivoa.net.

Comments

AndreaPreiteMartinez : suggested changes to the list:

1. suppress instr.filter.transm, replaced by phys.transmission;instr.filter

2. change instr.filter into a secondary word (flag S)

AlbertoMicol - 16 Sep 2005:

3. Suppress em.wl.central

Rationale:

em.wl.central exists, em.energy.central and em.freq.central don't. Wouldn't be better to remove it and use instead em.wl;stat.mean?

4. em.wl.effective

Similar, but not identical, to em.wl.central. Maybe effective and central should be added to (e.g.) stat?

PierreDidelon - 19 Sep 2005

somethings seem to miss in UCD1+, even compared to UCD1. for example

5. considering polarization in UCD1 we found POL_FLUX_LCP, POL_FLUX_LINEAR, POL_FLUX_RCP corresponding in UCD1+ (http://vizier.u-strasbg.fr/UCD/ucd1-ucd1p.txt) to ... phot.fluxDens even not a polarization, phys.polarization at least would be preferable. And it would be nice to introduce something more specific like phys.polarization.linear and phys.polarization.circular.

Similarly for POL_STOKES_I, POL_STOKES_Q, POL_STOKES_U, POL_STOKES_V only phys.polarization.stokes exists, it may be worthwhile introducing phys.polarization.stokes.I...

and even for new word introduced the tree is not enough developped

6. pos.bodyrc need to be extend to pos.bodyrc.lat, pos.bodyrc.lon, pos.bodyrc.alt and pos.bodyrc.dist

comments from PatricioOrtiz

* file http://vizier.u-strasbg.fr/UCD/ucd1-ucd1p.txt has one type in

SPECT_EQ-WIDTH spect.line.eqwidth

It should be spect.line.eqWidth.

* The following deprecated terms still appear in the list:

phot.fluxDens still in the list

phot.fluxDens.sb still in the list

phys.massYield still in the list

* The definition of arith.ratio can be used with quantities with different UCDs, eg, axis ratio: semi-major and semi-minor axes have different UCDs. Although the new UCD phys.size;arith.ratio doesn't make it clear that we're dealing with an axis ratio, we could be comparing planet sizes... worrisome

* em.line... drop molecular, so far only atomic lines are mentioned, unless molecular lines are to be added to the list.

S | instr.pixel | Pixel S | instr.plate | Photographic plate could be better off as Q

* pos.resolution... despite that most astronomical resolution is angular, there are other resolutions in distance, eg, solar and planetary phenomenae, and quite possibly a resolution in the distance scale. Simplifying too much could be dangerous in the long run. Furthermore, the angular resolution seems to me a quantity more related to the instrument than an intrinsic property of the object position in space.

* seems to me that instr.seeing should become part of the obs.atmos family... hold on,

* S | obs.field | Region covered by the observation Does the explanation encompass field of view? The equivalences with UCD1 doesn't seem to show that.

* I agree with Pierre that the section on polarization has been oversimplified

* phys.gravity: gravity is more than surface gravity, as it could be measured around any * objcted at any distance from the surphace, and the ones doing gravitational waves experiments may find this too limiting.

* Are numbers permitted in atoms? This: phys.mass.light may look much better as phys.mass2ligth or phys.massToLight, light is not a property of mass.

* People still quote "major axis" and "minor axis"... how do we fit this with phys.size.smajAxis and phys.size.sminAxis ?

* temperature: people modelling interiors might want a few more flavours of temperature.

* Q | pos.earth.altitude | Altitude, height above the Earth's surface

Do we really mean Earth's surface, as in an airborne apparatus or above sea level (to quote how high an observatory is?)

* time.x.start, and time.x.end . exposure is fine, observation is fine, what about a phenomenon? eg, a solar flare? What about start and end of a phenomenon at different levels of intensity/importance?

* in the area of photometry and color indices, how would I assign a UCD, and later on recognize without having to sort through a ton of meta-data a color index formed with two HST filters? Or Gunn filters? Just to name two of the commonly used systems today and left out of the list.

If it's felt that there are too many UCDs in the phot field, at least leave the root of the different photometric systems to avoid sorting irrelevant data when one is digging a registry for Cousins V-I!!