Boxes and Polygons in ADQL/STC. Questions and recommendation.

[Tom McGlynn]

Roy Williams wrote:
> It seems that the region specification does not support the RA/Dec 
> limits, or the Glon/Glat limits, etc etc. All polygon boundaries in ADQL 
> Region are great circles.
> -- Is that correct?
>
> Therefore I assume the recommendation will say that such regions should 
> NOT be implemented with ADQL Region, but should be implemented directly 
> in the SQL query like this:
>     RA between 200 and 210 and Dec between 20 and 30.
> -- Is that correct?
>
>   

I think so.  There is one issue that might make it nice to have a 
special function for this kind of box: the wrapping of longitude 
values.  E.g.,  if I want the 20x20 box from 350 to 10 degrees in lon 
and -10 to 10 in lat, the syntax is different than for the region from 
330-350 in lon.  So it would be nice to have some syntax -- say rect -- 
which would allow users to specify

    rect(350,10,-10,10) == rect(-10,10, -10,10) == rect(350,370,-10,10)

This allows users to specify the bounds consistently in whatever way 
that is convenient to them.  It can also handle the housekeeping to do 
this right (e.g., it would handle cases where the longitude is <0 or 
 >360).  Otherwise there will be problems with tables that use longitude 
values outside the canonical range.   We can say that's user error, but 
I know that we (i.e., the HEASARC) have at least some out of range values.

    Tom