TAP 1.1 comments

[Walter Landry]

Patrick Dowler <pdowler.cadc at gmail.com> wrote:
> comments below
> 
> On 8 May 2016 at 16:55, Walter Landry <wlandry at caltech.edu> wrote:
>> Hi Everyone,
>>
>> Here are some comments on the TAP 1.1 proposal.
>>
>> 1) The text proposes
>>
>>      INTERSECTS and CONTAINS are required. POINT, CIRCLE, and POLYGON
>>      are required. POINT (and point-valued columns) cannot be used as
>>      an argument to INTERSECTS.
>>
>>    What is the rationale for not allowing POINT's in INTERSECTS?
> 
> It is redundant with CONTAINS and iirc some people found INTERSECTS
> decaying to CONTAINS a pain to implement...

Ok.  That is surprising to me.  We already need to have cases for

  (circle,circle)
  (circle,polygon)
  (polygon,circle)
  (polygon,polygon)

So it would just be adding a few more cases.

  (point,point)
  (point,circle)
  (circle,point)
  (point,polygon)
  (polygon,point)

The implementations could just forward themselves to the CONTAINS
algorithms.  It also is simpler for the user, since they do not have
to remember the order of arguments required by CONTAINS.

>> 2) The text says
>>
>>      A query with MAXREC=0 can be used with a simple query
>>      (e.g. SELECT * FROM some_table) to extract and examine the
>>      VOTable metadata (assuming FORMAT=votable). Note: in this version
>>      of TAP, this is the only mechanism to learn some of the detailed
>>      metadata, such as coordinate systems used.
>>
>>    I thought that TAP_SCHEMA.columns has all of that metadata?
> 
> There is no coordinate system metadata in the tap_schema.

Can we add it?

Cheers,
Walter Landry