DALI vocabulary URL

[Markus Demleitner]

Dear DAL WG,

I just stumbled across a problem in the DALI spec that somehow
slipped through to REC.  Here's the gist:

Section 2.3 "Examples: DALI-examples" proposes to use
ivo://ivoa.net/std/DALI#examples as the default vocabulary URL. That
is unfortunate as the actual terms in RDFa are generated through
concatenation, such that the terms that would actually end up in the
StandardsRegExt document (not that they're actually there) would look
like "examplesname", "examplescapability", etc.  

While this is not a major disaster since the vocab URI isn't really
intended to be evaluated by VO code -- if you pull something from an
examples endpoint, you just look at the terms in @property and be
done with it.  Generic RDF tools, though, will complete the URIs and
may try to do something with the funny terms, which will at least be
confusing.

Possible solutions:

(1) We could keep the notion that we're using StandardsRegExt records
to keep the examples vocabulary. In that case we should IMHO have a
document separate from DALI's, which would mean we should write an
erratum saying the vocab URL should be
ivo://ivoa.net/std/DALI-examples#. This is (essentially) what's in
the TAP Implementation Notes right now.

(2) After the (positive) datalink experience with RDF-enabled
vocabularies and because there's no (known) code using this anyway so
far, my personal take is that we shouldn't use StandardsRegExt for
that in the first place. Vocab URIs, if they resolve at all, should
resolve to something that RDF tools can do something with, and hence
I'd say we should write an erratum saying the default vocab URI would
be http://www.ivoa.net/rdf/examples (which is in parallel to what we
have in datalink now).

As we don't really expect our tools to evaluate vocab, all this is
IMHO less dramatic than it sounds.

I've put as much on a page I took the liberty to create,
http://wiki.ivoa.net/twiki/bin/view/IVOA/DALI-1_0-Next.

Opinions?


Cheers,

         Markus