WD for the Obscoredata model and its implementation on TAP

[Petr Skoda]

On Tue, 21 Dec 2010, Anita M. S. Richards wrote:

>
>> redshift) is already in the full model.  But ObsCore is a simplified
>> subset intended only for data discovery.

>> Fixing the units is essential for discovery, at least if we plan to
>> use TAP-ADQL expressions globally.  The primary requirement is that

> Why? Conversions are easy and don't even need trig !
>


I have to repeat again and clearly (maybe the previous mail was too 
detailed and long to be understood well) that I do not understand what 
kind of a discovery is supposed to be realized with ObsCore - If we are 
talking about catalogues, I would expect the logical step is to convert 
Vizier interface and many other published tables into ObsTAP - but it is 
not possible on many due to the limitation of Observables list.

If the Use cases are mentioned as a motivation for the whole work the 
current Observables do not allow to realize the Use case 2.3. 
Unfortunately the modification of use case 2.3 are not possible to realize 
as well, but most people would not ask for Emission line width but Height
and one of the most usefull one would be (not only in stellar but for AGNs 
as well) :

Emission line height relative to continuum > 0   (i.e. object has an 
emmision)

In general I think there is a large disproportion between the quite 
complex description of Observation and Characterization (in table starting 
on p.15 in a draft) and very short and ad-hoc defined (and I must say - 
Radio and X-ray oriented ) selection of some "randomly selected" variables 
in Observables axis given in table on p. 41.

IMHO it is too short-sighted to define some restrictive list of a 
variables that should be the core information for making new discoveries 
of natural phenomena ;-)

I am missing here the one of core principle of VO infrastructure- the 
extensibility.

Or I have to apologize if I did not understand well the sentence in 
C.5.1.4.:
"The POSSIBLE UCD values are part of the UCD1+ vocabulary [9]"
and another sentence:
Table C.5.1.4 provides a list of POSSIBLE triplets ....

If this is just hinting in the table what kind of values may be expected 
(i.e. it is only an EXAMPLE of SOME observables) forget my objections 
expressed above.

I will understand that I can give any valid UCD1+ from relevant Standard 
[9] - it seems to be quite exhaustive and well scientifically based list 
with the possibility of future extensions (but still under strict control)
Then I would understand the text in 4.19 "The o_fluxucd collumn contains a 
valid UCD FROM the controlled vocabulary [9] describing .....



But if the word POSSIBLE means - only one from the set given in table 
(i.e. the enumerated parameter list of observables in left collumn of the 
table), I think that Observables part of a proposed Obscore WD should be 
subjected to more fundamental discussions about its purpose.

Anyway this ambiguity should not appear in the fundamental standard.


Cheers,

Petr

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*  Petr Skoda                         Phone : +420-323-649201, ext. 361 *
*  Stellar Department                         +420-323-620361           *
*  Astronomical Institute AS CR       Fax   : +420-323-620250           *
*  251 65 Ondrejov                    e-mail: skoda at sunstel.asu.cas.cz  *
*  Czech Republic                                                       *
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