Characterising URL columns

[Mark Taylor]

Francois,

On Thu, 1 Feb 2018, François Bonnarel wrote:

> I gave talks on this topic both in ShanhaI and Santiago meetings, following
> the ASTERICS discussion.
> 
>     See
> http://wiki.ivoa.net/internal/IVOA/InterOpOct2017DAL/DataLinkSolution.pdf

Thank you, that's an interesting discussion.  I obviously wasn't
thinking hard enough about datalink in Santiago or Shanghai to take
it in.

>     We prefer either the LINK solution exposed in the talk or if there is
> variation of the output the ObsCore-like solution with two Fields and utypes.

The LINK solution however, if I understand correctly, is not
standards-based.  It appears to rely on the LINK substitution syntax
described in VOTable Appendix A.1, annotated:

    "The definitions enclosed in this appendix are *not* part of
     VOTable 1.1, but are considered as candidates for VOTable
     improvements."

I believe this non-standard syntax is understood by Aladin, but not by
other VOTable clients.

Mark

--
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-9288776  http://www.star.bris.ac.uk/~mbt/