Core vs Extensions in data services

[Benjamin Gufler]

Hi Kona,

On 2006-11-14 13:57, Kona Andrews wrote:
> We have no objection to services providing flexible subsets of ADQL;

Neither have I.

> it's just that we don't believe the *language definition* is the right
> place to put a distinction/set of distinctions that apply to *services*.

I agree on that too.

> The IVOA is currently developing a capability mechanism to describe 
> what services can do, and I think capabilities are the right place to 
> describe modular subsets of ADQL that services might support. 

And I also agree on that.
What I was proposing in my mail yesterday is just a modular design of
the language (in the description as well as in the BNF), with names for
the modules. That way, each service would be able to choose the language
modules sustained necessary, without having to specify a restricted
version of the language's BNF (which would lead to inconsistencies if
the BNF of the language itself changes).
So, it's not defining "core" and "extension(s)" within the language, but
just providing:
* a more comfortable way of restricting the language for the services
* and probably a more consistent image of the language.

Benjamin
-- 
Dipl.-Inf. Benjamin Gufler       Lehrstuhl Informatik III
Tel. +49 89 289-17276            Fax +49 89 289-17263
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