RFC period for Characteristion DM has finished

[Pedro Osuna]

Dear all,


please find attached my comments to the Char DM.

I am not sure I am popping at the right time in this case (Mireille's  
mail does not say whether it did go to the TCG already or otherwise)  
so please forgive me if I am at the wrong timing.


Characterisation Data Model comments
===============================

The concepts in the document apply very well to the description  
(Characterisation) of, for instance, an observation. There is a  
clever separation into axes with different properties, which makes  
the complete characterisation possible with few parameters. For  
instance, the table in page 9 is very useful to identify correctly  
the concepts for a proper description of a "data set". The figure 2  
on the different levels of description is also very enlightening.

There are some points however that,not being showstoppers for the  
Recommendation process, should be considered for improvement, whether  
in this version or subsequent ones. Other issues are probably more  
editing than any other thing.

- in pg.3 reference is done to the Observation DM. However, it looks  
like not much work has been going on on the Observation DM. Is the  
Observation DM going to go ahead, or is it going to be "superseded"  
by the Characterisation DM globally?. In the former case (Obs DM  
disappearing), the Char DM should contain all the info that is  
currently on the Obs DM. In the latter, the difference (or  
complementarities) between the two should be briefly mentioned.

- in pg. 10 (point 3.4.1) mention is done to a combination of UCD and  
units to "ensure uniqueness and recognition by standard software".  
This issue has been treated many times, and at the last Beijing  
meeting it was finally recognised that a set of "BIYECTIVE UTYPES"  
should be defined for Data Models to be understood. This biyective- 
utypes were given the name "UFIs" by Jonathan. Despite the fact that  
they are undefined yet, they resemble _very closely_ the Object  
Oriented technology attribute naming, i.e., names constructed by dots  
in between class names. The issue of how to mention actions in the  
UFIs is also an important issue and a small team has been created to  
deal with these things (although admittedly, not started to work on  
it yet). Therefore, this paragraph should either contain a reference  
to that, or remove the first paragraph.

- the whole list of attributes in the Data Model should be clearly  
made explicit in the document. They should normally correspond to  
what has been called UTypes during all this time, and they should be  
inside the document, and not in a separate one. In particular, the  
UTypes should clearly reflect the UML structure of the DM. The UML is  
missing a "top level" diagram, where inheritances and associations  
are clearly seen. Also, the "Axis vs Properties" issue can be solved  
through proper UML modeling of the DM, and should be done so, in my  
opinion. Leaving the possibility to traverse the tree upside down  
(Axis to Properties) or the other way around might make the model  
unworkable for software handling. The UML and its attributes should  
be reviewed.

- mention is done in 4.4 of the Quantity DM. In my understanding, the  
Quantity DM effort has been discontinued by the DM group. If this is  
the case, the reference should be removed. Otherwise, a more detailed  
reference of how the Quantity DM is affecting this document should be  
made explicit.

- point 5.2 goes again to the UType creation. UTypes (or UFIs in our  
more "modern" view after Beijing) should not have repetitions in  
their names. Different model classes don't need to have the name of  
the parent in their name. In any case, the whole list of the UFIs (or  
UTypes) should be given in the document with a clear mapping 1 to 1  
to the UML diagram that represents them. The Spectral DM could be a  
good example of how this can be done.


That's all.
Cheers,
P.


On Jul 5, 2007, at 3:15 PM, Mireille Louys wrote:

> Dear IVOA members,
>
> The RFC period for comments for the Characterisation Data model  
> ended yesterday, after 5 weeks .
> This Data Model took quite a long time to get mature, and has been  
> presented in Interop meetings at
> different stages.
> People interested gave their comments and provided good hints all  
> along the different development phases.
>
>  Its scope has been divided to provide two versions of the Model:
> - the current 1.11 version for data queries and all purpose data  
> analysis
> - the next version will describe more refined metadata for complex  
> observations, sensitivity functions,
> resolution variations , etc...
>
> Comments on the RFC page are not numerous but I do not want to  
> delay the
> recommendation process any longer.
>
> It is time for me to pass it to the TCG group to review the document.
>
> Thanks ,
> Mireille Louys, DM Chair
>
>
> -- 
> --------------------------------------------------------------
>
>  Mireille LOUYS          mailto: Mireille.Louys at astro.u-strasbg.fr
>
> L S I I T                       &     CDS,
> Ecole Nationale Superieure            Observatoire de Strasbourg
> de Physique de Strasbourg,            11, Rue de l'Universite
> Boulevard Sébastien Brant, BP 10413   67000 STRASBOURG
> 67412 ILLKIRCH Cedex       	      Tel: +33 3 90 24 24 34
> ---------------------------------------------------------------
>
>
>



_________________________________________
Pedro Osuna Alcalaya

European Space Agency (ESA)
European Space Astronomy Centre (ESAC)
Research and Scientific Support Department (RSSD)
Astronomy Science Operations Division (SCI-SD)
e-mail: Pedro.Osuna at esa.int
Tel + 34 91 813 13 14    Fax: +34 91 813 11 72
_________________________________________
European Space Astronomy Centre (ESAC)
P.O. Box 50727
E-28080 Villafranca del Castillo
MADRID - SPAIN




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