Datalink Feedback VI: Semantics

[Mark Taylor]

On Fri, 25 Apr 2014, Markus Demleitner wrote:

> Dear list,
> 
> On Thu, Apr 24, 2014 at 09:29:43AM -0700, Patrick Dowler wrote:
> > Q. I did create a table with a column named "property" in postgresql
> > and sybase with no issues and didn't find it in the list of SQL
> > reserved words I checked... does anyone anticipate issues renaming
> > the "semantics" field to "property"?
> 
> A quick interaction with the search engine of my choice would suggest
> property is a safe column name.  
> 
> Still, if everyone could just briefly run
> 
>   create temp table autodropped (property real)

mysql OK ("create temporary table xx (property real);").

> > Q. Where do we specify the process for updating the vocabulary
> > itself? Is that something Semantics WG would have a general policy
> > about?
> 
> Ah well.  The precedent we have is the UCD addition process, for
> which there's a standard of its own, and given that AFAIK nobody has
> even tried it I suspect that's not a particularly good precedent.

I'll note another relevant precedent. 

For SAMP the semantic content comes in the form of MTypes,
which are effectively RPC definitions (procedure name, arguments,
return values, and semantic intent).  The "core" MTypes
(mostly associated with hub and client lifecycle) are defined
in the SAMP standard.  All the others (the ones that make SAMP
useful, things like exchaning tables, images, sky positions)
are simply listed on a wiki page
(http://wiki.ivoa.net/twiki/bin/view/IVOA/SampMTypes).
There is no formally defined process for updating this list,
but informally people make suggestions on the mailing list,
and if nobody has objections, they just edit the page.

This procedure is alluded to in the section 6.3 of the SAMP standard
(http://www.ivoa.net/documents/SAMP/20120411/REC-SAMP-1.3-20120411.html#tth_sEc6.3):

   Since addition of new MTypes is expected to be ongoing, MTypes from
   this broader vocabulary will be documented outside of this document
   to avoid the administrative overhead and delay associated with the
   IVOA Recommendation Track [20]. At time of writing, the procedures
   for maintaining the list of publicly-agreed MTypes are quite
   informal. These procedures remain under review, however the current
   list and details of best practice for adding to it are, and will
   remain, available in some form from the URL http://www.ivoa.net/samp/.

The language in the standard deliberately leaves open the possibility
that we might adopt a more formal process in the future, but up till
now the very informal process I've described has served us pretty well,
and certainly better than having to go through the standards track.

Now I'm not pushing this as suitable for the datalink case
(I haven't been following the discussion closely enough to understand
the requirements), but it may be useful to reflect that,
especially in a small community like IVOA members actively interested
in a given standard, very lightweight processes can work well.

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/