Identification model in VO Spectrum Model

[Doug Tody]

Hi Alberto -

On Wed, 25 Oct 2006, Alberto Micol wrote:
> Wouldn't, hence, be possible to specify (in the protocol/DM)
> the  different available contexts (adding for example an enumerated
> CONTEXT attribute), and to define for each of them the proper
> mandatory/optional/whatever fields?
>
> With that, clients will be able to specialise on a given context
> based on solid grounds, and I find this possibility extremely valuable.
>
> Someone could argue that we cannot imagine all the possible usages
> of a DM a priori; true! but on the other hand, as soon as someone comes
> up with a new context, it will be not difficult to include it in the
> next release.

Frankly, I think it is pointless to try to specify in a general data
model what is required/optional (except maybe for direct data analysis
upon a dataset instance)); this needs to be done for each specific
application of the data model.  The SSA protocol is one such case,
although even here there are additional contexts for different types of
data or services.  It is difficult to deal with all of these without
overly complicating the specification, however we have tried to do
so by defining protocol-wide requirements with additional written
narrative mentioning the special cases or contexts.

It would be good to move this discussion to a more concrete level;
I suggest reviewing the protocol document and commenting on what is
required for a minimally or fully compliant service for the specific
use-case of data discovery and selection.  (Followups on this specific
topic should go to the DAL list).

 	- Doug