[ObsCoreRFC]Minutes of the telco Monday June 6

[Arnold Rots]

Well, that's not really clear to me.
Are you saying that it is unwise to include optional columns in a
query, because it may cause them to error out?
Then why do we bother with optional items?
It seems to me that their use is discouraged. By not specifying how
servers should handle them we render them useless, don't we?

Cheers,

  - Arnold


Patrick Dowler wrote:
[ Charset ISO-8859-1 unsupported, converting... ]
> 
> 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/T?l: (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
> 
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Arnold H. Rots                                Chandra X-ray Science Center
Smithsonian Astrophysical Observatory                tel:  +1 617 496 7701
60 Garden Street, MS 67                              fax:  +1 617 495 7356
Cambridge, MA 02138                             arots at head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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