Product-type as a SKOS vocabulary

[Markus Demleitner]

Dear Semantics WG,

for Datalink 1.1 (which will be going to RFC fairly soon, I think),
we ought to have the vocabulary of data product types (spectra, time
series, images ...) ready.  At the last interop, I had suggested that
after a by and large failed attempt in spring we ought to have a SKOS
vocabulary for that; cf.
https://wiki.ivoa.net/internal/IVOA/InterOpNov2021Sem/product-type.pdf.

I have now prepared this vocabulary based on what obscore lists, plus
the dynamical spectrum that Baptiste has asked for.  Please have a look:

https://www.ivoa.net/rdf/product-type/

Dynamical-spectrum shows where this is going: If you search for any
of timeseries or spectrum and have term expansion on, you will get
dynamical spectra, too (Baptiste: do you perhaps have some of these
in an obscore table served through a DaCHS that already has the
gavo_vocmatch UDF?  That would be a nice demo).

If you have product types *in obscore services* (or perhaps those
new-fangled Datalink content qualifiers) that ought to go in here
before we go to DAL and the TCG, let me know; at this point we're
still in the vocabulary construction phase, which means it's easy in
(and easy out as well, if someone disagrees with a term, whereas a
non-preliminary term in an accepted vocabulary cannot vanish[1]).

Opinions?  (To give you an idea of the time frame I'm aiming for: My
current plan is to push this to DAL and the TCG by mid-December so we
won't hold up the Datalink RFC when it comes).

         -- Markus

[1] Well, in this particular case, I think we can't pull any of the
obscore terms. However, I can't lie: If I dared, I'd have thrown out
measurements on grounds of insufficient definition.  As always, it's
as important to say what a concept covers as it is to say what it
does not cover.