More comments on SimDM and the Nara Interop

[Miguel Cerviño]

Hello all

Thanks for upload the presentations in the wiki!! 

I send this mail to dm and theory, just waiting to the RFC will be open
(when it will we open we should send the mail to interop at ivoa.net isn't it?
I suppose that I will receive a mail from that list when the RFC will we officially open)
Please, let me know if this mail must be send to interop at ivoa.net
to forward the mail if it is the correct place)

I just want to make two comments on the presentations (in theory sessions) and a general one.

a) In 1st Herve talk, slide 11:

"SimDM and Access to the data

Comment: “the model includes some access data fields (Sect 4.7 and 4.8 in  •
particular), Following the SSAP it is the access protocol which includes its 
own data model for access spectra.”

Answer: Right. But SimDM will be used by SimDAL. See Gerard’s talk on  •
Friday session (SimTAP)

 Reasons: 
- there is no agreement in the ‘theory’ community (as a whole or even astronomical  
part of it) for a common data format (no real equivalent to FITS adopted by IAU)
- when he/she will access the data through a  need to specify what the user will find  
SimDAL service

Actions: none"

I do not understand the given reasons: a there is no problem with the data Format
In fact the use of VOTables solves the format problem as far as the fields of the data file
described whatever the format. 

I just wondering about applications that access theoretical spectra like VOSpec.
Do you mean is that VOSpec must do a SimDAL implementation to access 
theoretical spectra when it have access to theoretical spectra YET without
it? Will be SimDAL the only way to access simulations even if they are ALREADY 
working ways to access them? Must Vizier make a SimDM/SimDAL
implementation provide access to the published tables with theoretical results
like the isochrones they provide?

Is it not a bit overkilling?

(Again, I think that the issue is solve easily if SimDM just provide a data model to describe the
data that can be translated in a VOTable, and if SimDAL provide its own DataModel for access
in a similar way that  SSAP does, although it is not considered (slide 7).


b) Regarding the last slit in 1st Herve Talk answering the comments send to the mailing list.
In particular in the last slide

"Border line cases?

Comment: can a collection of empirical/observed/theoretical tracks/spectra  •
be described by SimDM"

First, as quoted in my first e-mail, these "border-line" cases are 90% of scientific 
use of theoretical data. I really do not understand how it fits with the IVOA exec
guideline of build-up the VO in a way astronomer use it.

Second, Herve use, and I acknowledge, the example of Miles library (Vazdekis et al. 2009)
as example of SimDM. 
In October I spend a 3 days meeting with IAC people (i.e. Vazdekis) trying to address this issue
(I send an e-mail to the "tiger-team" on the Theory group on that, also of a presentation about in
Victoria in the last Interop). We did not find a solution to make the quoted implementation for
the service MILES people want to provide. Actually, I wanted to test if it can be implemented using SimDM
and present it in this interop, but it is still a work in progress (where the service providers, i.e. Vazdekis et al,
involved).


I strongly acknowledge if you can send me how the implementation has been done as quoted in the slide
because I am lost with it an I would not like to re-invent the well ;)

Note: I just follow  the DRY (don't repeat yourself) and DIE (Duplication is evil) principles for 
software development; take a look to:
http://en.wikipedia.org/wiki/Don't_repeat_yourself

which I consider a very good practice.


c) A final comment. I think that at some point we are forgetting the "KISS principle"
(keep it simple and straightforward) that has been proved to work better principle for software development

http://en.wikipedia.org/wiki/KISS_principle

Maybe it is interesting to began to think about it...

Cheers and nice back to your countries

Miguel