Datalink vocabulary extension: sibling?

[Markus Demleitner]

Dear Apps,

Over in DAL, we've tried define a new concept in the datalink
vocabulary -- see
http://mail.ivoa.net/pipermail/dal/2020-February/008261.html.

The use case that started this is that the Gaia astrometry satellite
produces spectra and time series for a subset of the objects it
measures, and the idea is to use datalink to link the files to
catalogue rows using datalink.

The question essentially is: What is "the" relationship between the
astrometric record and the spectra (the quotes are there because
there are of course many such relationships, but we'd like to find
one that's at the same time characteristic and generalisable)?  

And more importantly: What are other cases like that, and what would
applications like to see so they can display these extra links at the
right moment (and not display them when inappropriate)?  That's why
I'm here: I'd be grateful for application writers' thoughts about our
(Semantics) problem.


The thread above somewhat petered out when considering two
alternatives:

#sibling -- essentially, this marks artefacts that came up from the
same basic measurement as #this; it nicely complements #progenitor
and #derivation that we already have in datalink/core.  Against it it
has been argued that it's not very intuitive to people who don't
think in provenance terms too much.  And that it perhaps is a concept
that's not very useful in practice (i.e., doesn't let clients do
things users would like them to do).

#see-also -- the idea is that it's "data people might be interested
in when looking at #this".  The trouble is that once I try to have a
clear definition for what this actually means I fail.  You see,
essentially all datalink terms would fall under #see-also, and I
couldn't find a good criterion to exclude them.

So, if we do something along the lines see-also, it would have to be
see-also-if-X, where X could be,  perhaps, "scientifically exploiting
#this" or "you have found something interesting in #this and would
like to learn more about it" or whatever.  I think you'll agree that
these proposals are... uncovincing.

After this, I'm essentially back to #sibling, which is well-defined
and (IMHO) easy to explain, which, as concepts go, is great.  It's
also been useful *for publishing* in several other data collection,
such as when people did line maps for a spectral cube.

But is it useful *when consuming*, i.e., when doing user interfaces?
If you think it's not, what concept *would* be useful to you?  Do you
perhaps have an idea how a see-also-if-X concept could usefully be
built?

Thanks,

          Markus