TAP WD

[Patrick Dowler]

On Friday 03 July 2009 06:18:42 Mark Taylor wrote:
> 2.5: table upload
>    "The default mapping of data types are shown above (no arraysize
>    or xtype)".  I don't understand what the parenthesis means here -
>    arraysize and xtype are both listed in the table.
>
>    xtype values: the current draft of the VOTable 1.2 standard
>    defines two well-known values for the xtype attribute: "iso8601"
>    and "STC-S".  Should these be used in place of "adql:TIMESTAMP"
>    and "adql:POINT"/"adql:REGION"?  Not necessarily, but consider it.

The reason for adql:POINT and adql:REGION is that these types have distinct 
usage within ADQL and we need to unambiguously map FIELDs to columns of these 
types. If we were to use xtype="STC-S" for both, the column type would not be 
explicitly known by the client (e.g. to submit a query that correctly used 
POINTs or REGIONs from the uploaded table).

Given that, we opted to consistently define the types in terms of ADQL types 
(thus adql:TIMESTAMP).

PS-the exact meaning of the adql: prefix needs to be clarified once the VOTable 
1.2 document goes to RFC (possibly a job for the TCG to flag any inconsistency 
since we have so many dependent RFCs on the go). 

PPS-The ADQL types are also used in TAP_SCHEMA and in VODataService (optional) 
for column types

-- 

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