ADQL XMATCH

[Marco Molinaro]

Dear DAL members and ADQL fans,
to go on with the ADQL-2.1 working draft
one issue is left, from Sydney interop,
to be discussed.

In the DAL splinter at the interop
it was agreed to add an XMATCH function
of binary type and definition

1 = XMATCH(a,b,radius)

However no agreement was reached about
the 'a' and 'b' parameters, whether they
should be points (ADQL:POINT) or RA&Dec
couples (floating point values).

Both choices have advantages and disadvantages.
Points are more into the logic
of a sky cross-match but require geometric
types to be directly available to the DB.
Coordinates couples are directly available
in whatever DB and would also let the XMATCH
function work for non-orthodox coordinates
matching, but of course loosing the sky matching
logic.

As I said (also due to time constraints) no
agreement was found in Sydney.

What's your opinion on this, and why?

Cheers,
    Marco
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ivoa.net/pipermail/dal/attachments/20160209/826b20cc/attachment.html>