relatedResource/altIdentifer [was: VOResource PR #1]

[Markus Demleitner]

Gilles,

On Thu, Dec 08, 2022 at 11:52:47AM +0100, gilles landais wrote:
> For instance, in VizieR, we add authors without any additional information
> and we complete the information with the bibcode to link the journal
> (content.source in ivoa registry)
> The journal is not clearly specified.
> 
> We do the same for data coming from space agencies (for instance Gaia) - but
> in that case, the reference is not adapted and could be improved using
> relationship/relationshiptype.
> 
> eg:
> 
> <relationship>
>   <relationshipType>IsDerivedFrom</relationshipType>
>   <relatedResource altIdentifier="doi:10.5270/esa-qa4lep3">ESA Gaia
> DR3</relatedResource>
> </relationship>

Interesting.  For the record, relatedResource can already have an
ivoid (and that's when it's most useful, as with auxiliary
capabilities), so it stands to reason that other identifiers would
make sense, too, and in particular DOIs would be really nice when you
translate VOResource to DataCite (where relationships so far suck
because no DataCite client knows about IVOIDs).

Since we already have altIdentifier-s in vr:Resource and vr:Creator,
that would certainly also not require us to break new ground.
However, they are elements there, and that is by design: there could
could be multiple such identifiers (e.g., a DOI and a URI) for some
such resource.  It would feel a bit odd to have it as an attribute in
relatedResource when it's an element elsewhere.

On the other hand, having it an element here would let people have
multiple identifiers in the relationship, and that would be most
inconvenient when doing the RegTAP mapping -- which we would probably
want, as "what VO resources do you have for doi:10.5270/esa-qa4lep3?"
seems a reasonable discovery query.  Allowing multiple
altIdentifier-s would entail an extra table just for these, because
rr.alt_identifier only is for identifiers for the resource itself or
its creators.  Well, or we could use a string array in
rr.relationship.  Both options make me go yuck.

So... what if we defined relatedResource/altIdentifier as an element
and said maxOccurs=1?  Do people already have use cases that would
blow that up?

And Gilles, are you available as a guinea pig to write records having
such altIdentifiers?

Thanks,

              Markus