Characterising URL columns

[Mark Taylor]

On Thu, 1 Feb 2018, François Bonnarel wrote:

> Dear Mark,
> 
> 
> Le 01/02/2018 à 16:23, Mark Taylor a écrit :
> > 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.
> Yes  you are right. We need small changes in VOTABLE anyway (also because
> content-type doesn't admot the datalink value at the moment).
> 
> The templating could be pushed to the normalized section if everybody agrees

Hm.  This templated LINK thing does seem to be solving the same problem
that is solved by [DataLink section 4] Service Descriptors attached
to generic [non-DataLink section 3] VOTables.

Agreed it's more verbose, but I don't follow your point on slide 4
of the presentation above:
   "Not really adapted For One single constrained PARAM (ID=...) which
    is more like a templated URL"
- it seems perfectly feasible to use service descriptors like that.

--
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/