Voc in the VO 2 / remarks

[Markus Demleitner]

Dear Frederic,

On Wed, Jun 03, 2020 at 10:31:11AM +0200, Frederic V. Hessman wrote:
> 
> > On 3 Jun 2020, at 09:27, Markus Demleitner <msdemlei at ari.uni-heidelberg.de> wrote:
> >>       2 ) for the  same reason (incomplete discussion) "Preliminary" terms
> >> should not be set in the "official" vocabulary list even with the
> >> "preliminary" tag. Examples using those terms should be provided in
> >> prototype services or realistic example files.
> > 
> > [...]
> > Plausible examples IMHO aren't enough -- if there's no immediate need
> > for a term, we should wait until that immediate need comes up, at
> > which point we probably better understand the problem we're trying to
> > solve.
> 
> I don't agree.  François is thinking of Voc primarily as a system
> of ontologies - of data models - which of course need to be tightly
> constrained in order to be useful.  I agree with Markus that we
> need something simple and quickly useful.  For that reason, I think
> our goal has to be to support vocabularies as simple term lists
> with or without much ontological frill.  The usefulness of
> hierarchical (avoiding the term "ontogolical") information within a
> vocabulary depends on the use case.  A term list is most useful
> when the end-user easily finds the terms she needs.  If a useful

Well, I'd say "it depends".  See
http://ivoa.net/documents/Vocabularies/20200326/WD-Vocabularies-2.0-20200326.html#tth_sEc2.1
for the use cases that motivate much of this.  For one, some of them
really need trees (as rather strict is-a hierarchies) -- and in many
cases (think time scales or reference positions) not finding what
you're looking for is a rather clear case compared to "soft" cases
like the UAT.  When people are sure there's a hole in this way, I
strongly suspect it's more likely they can be bothered to put in a
VEP (or at least a mail so others make a VEP from it.

> term isn't present, the motivation to search for another vocabulary
> is modest (unless we provide simple tools that do this), the
> motivation to put up ones' own VO-compatible vocabulary as a fix is
> highly limited and the expectation that some external gremium will
> quickly add a term when asked is zero. This is why I wasn't so

And do you think these expectations cannot be changed?  Not even,
say, with some sufficiently prominent "Haven't found what you need?"
button in a corner of the browser?

I still have to confess that I've not really considered too much
the scenario that people unfamilar with the IVOA might find
themselves having to author VEPs.  I'd still rather think hard about
ways to make it easier for them to participate than to try to
anticipate their needs (and quarrel a lot about the anticipations and
fail in the end after all).

> happy when UAT turned out to be highly stripped down from the
> original IAU terms list.  If terms are rarely used - no, my VO app
> doesn't need the term "armillarly sphere" - does your computer
> really care?

The computer probably won't, but annotators will if there is too much
ambiguity ("do I use #progenitor or #upstream-in-provenance?"), and,
worse, several of these vocabularies will be reflected in code (e.g.,
transforming reference positions), and there, it's critical that it's
well understood what a meaning really is, and that these meanings are
as well tried-and-tested as we can make them.

Perhaps our small, very formal vocabularies really *are* something
very different from big, soft ("SKOS") vocabularies and the two
things shouldn't be regulated by a single document, or at least in
two very different ways.

But I'm still very convinced that the IVOA's general stance "show
implementations if you want something to be standardised" is a really
great idea.  I'd still hope that we can take that to vocabularies as
well.

        -- Markus