vo-dml for cube

[François Bonnarel]

Hi Omar
On 15/12/2015 19:08, Laurino, Omar wrote:
> Francois,
>
> On Tue, Dec 15, 2015 at 11:55 AM, François Bonnarel 
> <francois.bonnarel at astro.unistra.fr 
> <mailto:francois.bonnarel at astro.unistra.fr>> wrote:
>
>     PS : I am not considering here any kind of serialisation of these
>     VO-DML decscriptions (Object relational maaping, VOTABLE Mapping,
>     specific-stc2-xml-schema xml  documents, json, etc... ). this is
>     another story but the initial VO-DML description will constraint
>     the solution. 
>
>
> I mostly agree. However, one of the benefits of VO-DML is to have a 
> language that can easily be mapped to a variety of contexts, including 
> OO languages and relational databases, and so ORM. If variable length 
> arrays were impossible (or very hard) to treat in ORM, then they 
> should be left off the language, because they would be impossible (or 
> very hard) to treat in a fundamental set of implementations.
>
> But yes, the implementation details of how to map VO-DML model 
> instances to a serialization is a different topic. So for instance, a 
> model might call for a great number of Object Type instances, but 
> specific serialization or representation formats might allow more 
> efficiency, whether we are talking about Java objects or SQL tables, 
> or FITS. An image might have, in principle, an Object Type 
> representation for each pixel in an image, but a FITS representation 
> might factor out all the common metadata into a single representation 
> for all the pixel in the image.
I think I agree with all that
> I say in principle because I am not sure I can take a side in the 
> modeling part per se, so I don't have an opinion on whether a pixel 
> should be an Object Type or a Data Type, in this example.
It is really strange for me to have coefficients as independant Objects 
(instances of ObjectType).
       - Semantically a coefficient is basically just a number and 
become a coefficient only in the context of polynomial. And we want 
anything done for polynomials in the STC model to be independant of the 
order
       - As both Arnold and Laurent stated in different wordings one of 
the usage of UML (and attached VO-DML description) is generation of 
code. ObjectType will become classes and having instances of that for 
"coefficient" and "pixel" will lead to considerable overhead.

Cheers
François
>
> Omar.
>
>
> -- 
> Omar Laurino
> Smithsonian Astrophysical Observatory
> Harvard-Smithsonian Center for Astrophysics
> 100 Acorn Park Dr. R-377 MS-81
> 02140 Cambridge, MA
> (617) 495-7227

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ivoa.net/pipermail/dm/attachments/20151216/e35be471/attachment.html>