Collaboration on Source Catalogue DM, ADQL and SkyNodes

[Roy Williams]

Thank you Pedro, I am reassured that what you are doing is to connect 
up the different parts of the VO that already exist, rather than making 
a whole new way. This is very good.

I like your interpretation of the Data Model as a "view". If I might 
expand on my understanding a little?

(a) If I have a catalog (RoyCat) with an attribute RoyZ that is 
redshift, then I can (obviously) use ADQL like this
	select * from RoyCat where RoyZ >4

(b) BUT now I can build this virtual table, this view, called 
RoyCatViewedAsSourceDM, which is really the same table, and I can make 
ADQL like this
	select * from RoyCatViewedAsSourceDM where Redshift>4
where "Redshift" is your semantically-precise utype.

Finally, the story about the source identifier......
I am worried that the data model people will assume that the identifier 
can be an arbitrary 100-character string, but the database people will 
assume it is a 32-bit or 64-bit integer. This is my worry, and I hope 
you will make it clear in your document what is the nature of the 
identifier.

Roy

California Institute of Technology
626 395 3670
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