[VEP-003]: datalink/core#sibling

[Markus Demleitner]

Dear DAL, dear Semantics,

Following the discussions on VEP-001, its author François agreed to
first try with a VEP that only has the core term and to defer the
child terms intended for SAMP resolution until we've investigated
alternative solutions for that requirement in datalink.  Also, Pat's
remark that all data in a datalink document better be "associated"
suggested a change of terms.

Therefore, we've retired VEP-001 (there's a discussion of the details
in
https://volute.g-vo.org/svn/trunk/projects/semantics/veps/VEP-001.txt).

Instead, there's now VEP-003:

ocabulary: http://ivoa.net/rdf/datalink/core
Author: François Bonnarel, Markus Demleitner, msdemlei at ari.uni-heidelberg.de
Date: 2019-12-06
Supercedes: VEP-001

New Term: sibling
Action: Addition
Label: Sibling Data
Description: Data products derived from the same progenitor as #this.
  This could be a lightcure for an object catalog derived from repeated
  observations, the dataset processed using a different pipeline, or the
  like.
Used-in: 
  http://dc.g-vo.org/gaia/q2/tsdl/dlmeta?ID=ivo://org.gavo.dc/~?gaia/q2/199286482883072/BP
  This is GAVO's rendition of the Gaia DR2 epoch photometry, where
  users retrieve a time series in a specific band; the time series
  in the other bands are the siblings of that.

Rationale: 
  It is fairly common in complex pipelines that multiple data products
  result from a single observation.  Often, this is true even in a
  single pipeline step, and hence the data products are not in a
  progenitor-derivation relationship.  Still, researchers will want to
  know about these data products; for instance, while exploring a source
  in Gaia, a quick way to access epoch photometry or the RP/BP spectra
  is obviously valuable; such artefacts are not really progenitors of
  the catalog entry, though.  In such cases, #sibling (or perhaps one of
  its future child terms) should be used.

  Clients should offer #sibling links in a context of scientific
  exploitation of the dataset (as opposed to, say, debugging).


Opinions?  Comments?  

I'd suggest to keep this discusson on the DAL list.

Thanks,

           Markus