[ObsCoreRFC]Minutes of the telco Monday June 6

[Patrick Dowler]

The notion of "mandatory" in the ObsCore physical model (the table) is that 
the column must be there and thus the (ADQL) query will run successfully. 

Having said that, if an service provider simply adds the column (pol_states 
VARCHAR(32) and leaves all the values NULL, it will behave as you say below 
(unless of course the WHERE clause had "pol_states IS NULL" as that would 
potentially return rows :-)

So, the information is not mandatory: the presence of the column is mandatory. 
Now, for a TAP service to behave as you suggest below for columns they do not 
have in the table or view -- that would be very onerous to implement.

Hope that is clear,

Pat

On 2011-06-09 12:55:50 Arnold Rots wrote:
> 1. I puzzled over the comment on whether polarization information
> should be mandatory. The logic applied seems to lead to the assumption
> that all datasets that do not provide a particular optional item will
> return an error as soon as that item is in the query.
> I would have assumed that the behavior SHOULD be:
> - if a particular item in the SELECT clause is not available from a
> service, that service SHALL return a NULL value.
> - if a particular item in the WHERE clause is not available from a
> service, that service SHALL return an empty list of results.
> Under that assumption, there should not be any problem in making
> polarization optional.

-- 

Patrick Dowler
Tel/Tél: (250) 363-0044
Canadian Astronomy Data Centre
National Research Council Canada
5071 West Saanich Road
Victoria, BC V9E 2M7

Centre canadien de donnees astronomiques
Conseil national de recherches Canada
5071, chemin West Saanich
Victoria (C.-B.) V9E 2M7