database/votable data types

[Patrick Dowler]

I agree it is a reasonable thing to want to do and may, in some cases be 
a necessary thing to do to make the output tables valid and fully 
functional. I haven't run into such a case myself, but if I did I would 
likely have made the output use unicodeChar without feeling guilty :-)

In that sense, maybe "default" is a poor word choice and "typical" would 
have been better. I don't think we should mandate specific mappings 
because it we have specific RDBMS features on one side and VOTable 
features on the other, with TAP in the middle.

In my opinion, people should be able to extend the behaviour of services 
and go beyond the lowest-common-denominator of the standard. In TAP, 
that sometimes comes down to custom datatypes or unusual datatype 
mappings to votable. I think we should try to allow that.

So, definitely some clarification is needed, but I would say the answer 
to your question is intended to be "no, not required..."

Pat

On 04/06/14 02:49 AM, Mark Taylor wrote:
> Hi DAL (Pat?),
>
> I have a question about the intent of the table in sec 2.5 of TAP 1.0,
> which associates VOTable datatypes with database column types.
>
> The associated text says
>
>     "The default mapping of data types are shown [in the table]"
>
> but I'm not quite sure what "default" means in that case.
>
> My concrete question/example is this:
>
>     If a column declares itself with datatype VARCHAR in TAP_SCHEMA.columns,
>     is it REQUIRED to appear with datatype="char" in the VOTable output
>     of a query response?
>
> The reason this has come up is because Markus has some VARCHAR columns
> which appear as unicodeChar in VOTable output.  This is a reasonable
> thing to want to do, but I don't know if it's legal.  If not, this
> should be another item to address for future evolution of TAP;
> though it might get addressed in future evolution of VOTable if that
> happens.
>
> Mark
>
> --
> Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
> m.b.taylor at bris.ac.uk +44-117-9288776  http://www.star.bris.ac.uk/~mbt/
>

-- 

Patrick Dowler
Canadian Astronomy Data Centre
National Research Council Canada
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