ADQL XMATCH

[Alex Szalay]

We wrote a long paper about this with Tamas, and we are building the xmatch service with all these features 
Implemented by Laszlo Dobos. I will dig out the references shortly

--Alex


-----Original Message-----
From: dal-bounces at ivoa.net [mailto:dal-bounces at ivoa.net] On Behalf Of Markus Demleitner
Sent: Wednesday, February 10, 2016 1:54 AM
To: dal at ivoa.net
Subject: Re: ADQL XMATCH

Hi Alex,

On Tue, Feb 09, 2016 at 07:55:33PM +0000, Alex Szalay wrote:
> I agree with Tom, that this approach is completely flawed.  The notion 
> of a spatial crossmatch is not a logical value, but it is a posterior 
> likelihood, or at best a Bayes factor which can (and
> should) be combined with additional attributes like shape, flux, color 
> etc.

I always like it when something is based on a good theory, and sometimes a good theory explains why there appear to be no satisfying solutions to an existing problem[1].

So: based on a probabilistic analysis of crossmatching, do you have a proposal for how these concepts could be mapped into ADQL language elements?

Thanks,

        Markus


[1] which here is: everyone wants to do crossmatches, and what ADQL right now offers is the highly unpopular (and also boolean)

1=CONTAINS(POINT('ICRS', ra, dec), CIRCLE('ICRS', basera, basedec))