datatype values in TAP_SCHEMA.columns

[Mark Taylor]

Hi TAP implementers,

I've just noticed that there appears to be some confusion about the
values in the "datatype" column of table TAP_SCHEMA.columns.
Some services prefix these with a namespace:

   % stilts tapquery sync=true ocmd='clearparams *; tablename ""' adql='select max(table_name) as a_table, max(column_name) as a_column, datatype from TAP_SCHEMA.columns group by datatype' tapurl=http://www.cadc.hia.nrc.gc.ca/tap
   +--------------------+--------------------------+----------------+
   | a_table            | a_column                 | datatype       |
   +--------------------+--------------------------+----------------+
   | cfht.wideZ         | POS                      | adql:POINT     |
   | caom2.SIAv1        | position_scale           | votable:double |
   | ivoa.ObsCore       | Z_ML                     | adql:DOUBLE    |
   | ivoa.ObsCore       | provenance_lastExecuted  | adql:TIMESTAMP |
   | caom2.Plane        | time_axis_function_naxis | adql:BIGINT    |
   | ivoa.ObsCore       | s_region                 | adql:REGION    |
   | TAP_SCHEMA.tables  | utype                    | adql:VARCHAR   |
   | TAP_SCHEMA.columns | Z_FLAGS                  | adql:INTEGER   |
   | ivoa.ObsCore       | Z_PETRO_RADIUS           | adql:REAL      |
   | ivoa.ObsCore       | provenance_inputs        | adql:CLOB      |
   | caom2.SIAv1        | position_naxis           | votable:long   |
   +--------------------+--------------------------+----------------+

and others don't:

   % stilts tapquery sync=true ocmd='clearparams *; tablename ""' adql='select max(table_name) as a_table, max(column_name) as a_column, datatype from TAP_SCHEMA.columns group by datatype' tapurl=http://cdatest.cfa.harvard.edu/csctap 
   +------------+---------------------+----------+
   | a_table    | a_column            | datatype |
   +------------+---------------------+----------+
   | obi_source | var_sigma_w         | DOUBLE   |
   | obi_source | var_inter_hard_flag | INTEGER  |
   | obi_source | var_intra_index_w   | SMALLINT |
   | tables     | utype               | VARCHAR  |
   +------------+---------------------+----------+

My reading of TAP sec 2.6.3 is that the non-namespacers are right,
Those in the other camp include GAVO, CADC and ASDC.
I've talked to Markus, and he agrees that he appears to be
doing it wrong.

Am I (taplint) right in flagging use of namespace prefixes in this
context as an error, or can anybody who's doing it like that point
to justification in one of the standards?

A related issue is use of non-database type values (e.g. votable:long
in the above) in this column.  I think it's not legal (anyone disagree?),
but I've had a conversation with Pat about this in the past and I
think he has some reason for wanting them in there anyway.

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/