[QUANTITY] Data Model for Quantity v0.5

[Pierre Didelon]

Hi David,

the following is not very interesting certainly,
only to specify my feelings,
already expressed previously on the list.
As Alberto concerns seems to be approching mine,
I jumped into the discussion. Apologies for diversion.

sincerely yours,
Pierre

David Berry wrote:

> Pierre,
> 
> 
>>Well! it depends of the point of view.
>>Speaking of human species, starting from neolithic up to nowdays,
>>something like that occurs, and it is not evident if a jet fighter
>>project starting ab nihilo would have succed in any achievement.
>>We may be need a bicycle first, and once we understand everything on the subject
>>we can try a car, and then go on.
>>Moreover, people needing only bicycle are then not force to use a jet.
>>I am deeply in favour of a very pragmatic bicycle.
>>I am really afraid by the lunar rocket style of the actual quantity model,
> 
> 
> I think we are not starting from nothing, or anywhere near nothing. There
> are already developed systems in regular use around the world which are
> similar to the proposed Quantity model. It must surely make sense to

What are the premiss or forerunner in the astronomy field?
did some generic/general standard available for this purpose,
can VO adopts and use them for interoperability?

> build on the existing experience rather than throwing it all away and
> starting back at the "bicycle" stage. You never reach the aircraft
> stage if you keep on throwing away previous experience.

Yes, and previous experience in astronomy was astrores
(http://cdsweb.u-strasbg.fr/proj/astrores.htx), which more or less
give birth to VOTable, and ASU (http://vizier.u-strasbg.fr/doc/asu.html),
which AFAIU was "adapted" for cone search and so.
But improvement to this "pre-bicycle stage" must be performed, and
IMHO one major goal of Quantity would be to procure support
for this kind of problematic : ability to transmit simple parameters
sufficiently described (inside the VO frame).
It is why I feel that XML serialization is the most important
part of Quantity.
The actual Quantity even if quite reasonnable in comparaison
of some previous ideas on the list, seems to me really complicate
for very simple parameter exchange. The most simple qantity (ex. p25)
as the flavor of a degradated PARAM structure existing in VOTable!

Complete description of whatever astronomical data is not in the scope
of Quantity but preferably in Observation global view.
For tabular data VOTable exists, and it can be used for vectors
eventually if needed, and complete metadata is then available in there.
So the most evident "ecological territory" available for quantity
seems to be very restricted to "simple described parameters".
It is only my opinion obviously, share perhaps by few persons
and eventually by nobody.

> 
> 
>>and I certainly don't understand half of the document.
> 
> 
> This is the first problem to address. If people do not understand the
> document, it will be difficult to get useful discussion on the model
> itself. Comments welcome...
> 
> 
>>Does people who would use these data types (data providers/VO actors...?)
>>feel confortable with this very complex construction?
> 
> 
> If not, we need to know what specific aspects of the document or model
> are causing concern. Then we can attempt to clarify or simplify them.
> 

I am not an institutionnal representative,
so my opinion has no political weigth.
I am only a technical part waiting for common standards,
to eventually use them, instead of using ad hoc, private,
partial and imperfect definitions in my little corner.
So my comments are only the "feelings" of an eventual
simple/dummy user.

> 
>>The only thing, I think is promising (imho) is to forgot the implementation
>>(no mention of the data structure in term of data member or class attributes)
>>and concentrate on interface and method definition, leaving implementation
>>free and adjustable to the needs of any intervening party.
> 
> 
> Agreed.

one agreement at least! ;-)
> 
> David
> 
> ----------------------------------------------------------------------
> Dr David S. Berry    (dsb at ast.man.ac.uk)
> 
> STARLINK project		 |	Centre for Astrophysics
> (http://www.starlink.ac.uk/)	 |	University of Central Lancashire
> Rutherford Appleton Laboratory	 |	PRESTON
> DIDCOT				 |	United Kingdom
> United Kingdom			 |	PR1 2HE
> OX11 0QX                                Tel. 01772 893733
>                                              01257 273192
> 
> 

-- 
Pierre 
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