TAP document implementation issues. Section 2.6

[Patrick Dowler]

On Thursday 01 October 2009 17:28:20 Patrick Dowler wrote:
> On Thursday 01 October 2009 13:39:41 Douglas Tody wrote:
> > In our (partial so far) implementation of the TAP schema here we
> > created DBMS tables much like TAP_SCHEMA.tables and TAP_SCHEMA.columns.
> > We did use boolean for std,primary,indexed in the native DBMS tables.
> > I agree we should consider just using boolean in the TAP schema itself.
> > This was an oversight I think.
> 
> In clarifying this section I have made the datatypes of columns in the
> TAP_SCHEMA tables explicit. They are basically VARCHAR (but no size
>  specified) for everything except some in Columns: size is an INTEGER and
>  principal, indexed, and std are BOOLEAN.

Correcting myself:

We can't actually do this since ADQL does not have a BOOLEAN type. 

We could follow ADQL region function style and use integer, with 1 meaning 
true and 0 meaning false (CONTAINS and INTERSECTS return 0 or 1).

Alternatively, we could use CHAR(1) with values T and F. 

In either case, VOTable does have boolean so this is likely to cause 
confusion. The mapping table in sec 2.5 is bidirectional, but we cannot really 
specify a bidirectional mapping of boolean. 

Maybe TAP just cannot support VOTable boolean type? 

Arbitrary decision: I will go with INTEGER and 0 or 1 (for the flags in 
tap_schema.columns) and I will change the table in section 2.5 to say that 
VOTable boolean is not supported by TAP unless there is strong input to do 
something else (and very soon - see PS)

thanks in advance for help/support/ideas,

PS-My understanding is that TCG review has to start in the next couple of days 
in order to be completed before the interop... so I will need some input or 
will have to make an arbitrary decision in the next 24-36 hours. I also know 
some people are travelling to ADASS in Japan and are likely off-line.

-- 

Patrick Dowler
Tel/Tél: (250) 363-0044
Canadian Astronomy Data Centre
National Research Council Canada
5071 West Saanich Road
Victoria, BC V9E 2M7

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