SKOS concepts in VOTable

[Norman Gray]

Brian, hello.

On 2012 Jun 1, at 14:37, Brian Thomas wrote:

> Why aren't we considering simply importing parts of the RDF standard
> into VOTable schema? What about the "rdf:about" attribute into the
> VOTable standard? This would be unambigious in use (the rest of the
> world already defines and understands it), it could be made to allow for
> multiple semantic urls to be declared and it would conform to an existing
> standard and would be compatible with SKOS, as well as other forms of
> RDF like owl and because its namespaced, it would be trivial for downstream
> parsers to simply ignore it.

An interesting idea, but perhaps I'll let you try to sell that to the VOTable chair.

Mark, you may want to stop reading about here...

All the things you (Brian) say are true (one could also imagine a sort of VOTable RDFa), but:

  * The rdf:* elements look icky, and including them would require schema changes to avoid them breaking validation (which many people care about).  That's not going to fly, because it was an explicit principle of the current forced changes in forthcoming 1.3, that this wouldn't be an opportunity to embark on wholesale VOTable revisions: the proposed changes to link/@content-role are only acceptable because they require no schema changes, and no more than a usage note added to the relevant section of the document.

  * Also, I think your proposed changes are too precise!  There's been some pressure (mostly from the Theory IG) to get SKOS Concepts included somehow in VOTable, somewhere cognitively 'near' to utypes.  I'd like to see something here which is flexible enough that could in principle (though I wouldn't expect in practice) support UCDs and utypes, too.  Since UCDs, utypes and SKOS Concepts are all vague in different ways, the relationship between the LINK-annotated thing in the VOTable, and the 'type' is also necessarily vague, and the detailed semantics of the @content-role='type' link would be something like "has a type which is related to".  That would handle all of the cases, plus references to owl:Class.  This of course requires something more or less heuristic on the part of a reader, but that's no worse than the existing @ucd and @utype relationships, and at least we're up-front about it.

In other messages I've mentioned the @content-role='seealso' (or @content-role='doc').  The reason for suggesting that is so that if it were deemed important to add some further semantic information, however precise, then this would point to a source of that: the retrieved seealso document could include statements about the VOTable document and id-bearing elements within it, without restriction.

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK