Unified Content Descriptor Controlled Vocabulary RFC

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

In order to add a comment to the document, please edit this page and add your comment to the list below in the format used in ResourceMetadataRFC (include your WikiName so authors can contact you for further information). When the author(s) of the document have considered the comment, they will provide a response after the comment.

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)

Answer (by AndreaPreiteMartinez): suggestions accepted.

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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?

Answer (by AndreaPreiteMartinez):

the proposal to move the atoms "central" and "effective" to the stat tree can be discussed for the next issue of the controlled vocabulary. The reason why wl.central exists, while energy.central or frequency.central don't, is that "central wavelength" is a description of a quantity that is actually used (remember the bottom-up approach of the vocabulary). See, e.g. HST log or the wfpc2.

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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

Answer (by AndreaPreiteMartinez):

"phys.polarization" already exists. Atoms "linear"/"circular" can be introduced. The UCD "phys.polarization.Stokes" groups all Stokes parameters. It could be worthwhile introducing the different names of the parameters in the case they were used separately.

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6. pos.bodyrc need to be extend to pos.bodyrc.lat, pos.bodyrc.lon, pos.bodyrc.alt and pos.bodyrc.dist.
pos.precess, pos.eop, pos.eop.nutation really need extensions also.

Answer (by AndreaPreiteMartinez):

suggestions accepted for "pos.bodyrc". For the other, open to suggestions!

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comments from PatricioOrtiz

7. 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.

Answer (by AndreaPreiteMartinez): change accepted

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8. 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

Answer (by AndreaPreiteMartinez):

Yes, we say explicitly this in the document:

"Changes from v1.01 . The following words have been restored to their previous spelling (v1.00):

phot.fluDensity	phot.fluxDensity
phys.energDensity	phys.energyDensity
phys.mYield	phys.massYield

A note has been added to indicate that these words do not strictly comply with the UCD1+ Rec. "

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9. 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

Answer (by AndreaPreiteMartinez):

Indeed, so I suggest the introduction of the new word:

E | phys.size.AxisRatio          |  Axis ratio (a/b) or (b/a)

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

Answer (by AndreaPreiteMartinez):

this is a change in the description of a "word". Taken.

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11.

S | instr.pixel | Pixel

S | instr.plate | Photographic plate

could be better off as Q

Answer (by AndreaPreiteMartinez):

No, they are not quantities. Example: if we say "plate" we probably want to indicate some specific quantity related to that plate, e.g. its "name" (then we'll write: meta.main;instr.plate) or central coordinates (then : pos.eq.dec;instr.plate)...

Similarly for a "pixel".

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12. 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.

Answer (by AndreaPreiteMartinez):

Yes, "pos.resolution" might be misleading and indeed you may be right in the long run. We can modify it into "pos.angResolution".

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

14. 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.

Answer (by AndreaPreiteMartinez):

Indeed, it doesn't mean that.

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

Answer (by AndreaPreiteMartinez): See answer to comment #5.

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16. 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.

Answer (by AndreaPreiteMartinez):

this is a change in the description. Taken.

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17. 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.

Answer (by AndreaPreiteMartinez):

Right. Let's propose "phys.massToLight".

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

Answer (by AndreaPreiteMartinez):

In the present list we have:

phys.angSize	Angular size width diameter dimension extension major minor axis extraction radius
phys.angSize.smajAxis	angular size extent or extension of semi-major axis
phys.angSize.sminAxis	angular size extent or extension of semi-minor axis

where one can find all 4 combinations of "major,minor,semi". In the next version of the vocabulary we can decide, for instance, to introduce

phys.angSize.majAxis

phys.angSize.minAxis

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

Answer (by AndreaPreiteMartinez): open to suggestions!

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20. 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?)

Answer (by AndreaPreiteMartinez):

this is a change in the description. Yes, we mean above sea level. Taken.

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21. 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?

Answer (by AndreaPreiteMartinez): I think it would be a good idea to introduce

time.event.start/end

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22. 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!!

Answer (by AndreaPreiteMartinez):

In the next version of the vocabulary we can decide, for instance, to introduce "S" words indicating the photometric system (perhaps the right place is in the registry).

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-- PierreDidelon - 23 Sep 2005

23. It seems that pos.satellite is not very usefull now that pos.bodyrc is available. Moreover its equivalent in UCD1, POS_PLANETARY may have very strange usage (see http://cdsweb.u-strasbg.fr/UCD/cgi-bin/ucd_stats?leaf=POS_PLANETARY&query=Submit) like, among others, positions of spots on close binary system [in J/A+A/426/1001, Catalog of contact binary stars (Csizmadia+, 2004) (http://cdsweb.u-strasbg.fr/cgi-bin/VizieR-3?-source=34261001&-out=*POS_PLANETARY&-meta.ucd=u) which has nothing to do with PLANETARY stuff.

Answer (by AndreaPreiteMartinez):

I agree that "pos.satellite" is not only useless but misleading, or just "wrong"! Indeed its description is:

Position/coordinates of satellite or planet, not

Position/coordinates on satellite or planet.

It is as if we had to add "pos.star" or "pos.galaxy" to pos.eq.ra/dec of a star/galaxy!

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