Datalink vocabulary

[Markus Demleitner]

Dear DAL,

[taking the discussion from interop to DAL]

On Thu, Jul 31, 2014 at 08:54:43AM +0200, François Bonnarel wrote:
>     Thanks to Mireille, Laurent, Norman, Pat and Sarah the datalink
> vocabulary for semantics of the links in DataLink is now available
> here:
> http://www.ivoa.net/rdf/datalink/

One thing I notice is that the "self" thing I've advocated is missing
(to mark up the link to the primary dataset); however, I think it is
important, as for some of the existing datalink prototypes, access to
the full dataset is *only* possible through datalink, and clients
need a robust way to discover what link to use to retrieve it.

I'd also like to make the terms more self-contained, as I expect most
clients will, at least initially, have to work on these exclusively
rather than have our little ontology.  And of course, neither
publishers nor users can be expected, in general, to know the model.
So, they'd not see #preview/image, they'd just see #image, and they'd
be confused to see what's coming back is a preview.  This, in
particular, concerns

image (-> preview-image)
plot  (-> preview-plot)
proprietary (-> ? -- I'm pretty sure rather than give that publishers
  should be encouraged to use the other categories -- after all, all
  data conform to *some* data model; so, they should rather say "this
  is a characterisation" than "this is in some proprietary data
  model)

I'm also not sure that "characterization" is a good term for char
data *in IVOA form*.  obscore and imagedm are less generic and thus
might be ok (although even there I wouldn't mind an "ivo-" prefix).
I'd much prefer "ivo-c14n" or something like that, to allow people to
characterize some other form of c14n data.

Also, without having read the Turtle specs, I'm pretty sure the #
shouldn't be part of the names in the TTL file; the way this is
written would imply, I guess, that the full form of these terms would
be http://www.ivoa.net/rdf/datalink##preview -- which we certainly don't
want.  Norman?

Otherwise, I like it.

Cheers,

        Markus