Arrays in TAP_SCHEMA

[Mark Taylor]

Alberto,

On Wed, 31 May 2017, alberto micol wrote:

> My use case regarding arraysize=“2" in TAP is here described.
> 
> SSA 1.1 requires, in the VOTable output, a single field for the spatial location,
> expressed as:
> <FIELD ID="SpatialLocation" name="SpatialLocation" datatype=“double" ucd="pos.eq" utype="ssa:Char.SpatialAxis.Coverage.Location.Value" arraysize="2" unit=“deg”>
> 
> At ESO we are implementing SSA on top of TAP. 

I agree with Markus that the issue we're discussing here shouldn't
block your development of a TAP-based SSA service.  It's true that
TAP_SCHEMA.columns may not provide an unambiguous report of the
SpatialLocation dimensionality, but that doesn't mean you can't
emit tables with 2-element arrays in that column, and since that
column's dimensionality is defined by SSA, then SSA-aware clients
don't need to look at the TAP_SCHEMA to understand it anyway.

> I therefore created the spatial location column in the TAP_SCHEMA.columns table declaring size=2,
> but TAP does not translate this information into the (naively) expected arraysize=“2”,
> for the reasons that Gregory explained.
> 
> Hence, we are stack with the development of the ESO SSAP...
> unless some smart DAL person comes up with a solution!

It sounds like you might be complaining here about an implementation
issue (you are unable to get your TAP server software to emit 2-element
arrays in a certain column) rather than deficiencies in the standard.
That may still require something to get fixed, but not at the DAL level.

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/