Single or collection resources

[Ray Plante]

On Wed, 5 Aug 2009, Alberto Micol wrote:
> The downside: it might happen that several entries for the same SIAP are 
> returned by the registry
> and a client could then issue many identical queries to the same SIAP service
> (but that could be easily avoided by a "distinct  IVOA Identifier" ).

Just to remind ourselves, the notion of using shared identifiers to 
indicate copies of the same collection gets thorny very quickly.  One gets 
into questions what constitutes a "mirror" (what is equivalence), 
particularly when they are curated by different institutions.

Also, Markus presents a slightly different take on this problem: a 
collection that is an aggregate of other separately identified 
collections.

cheers,
Ray