IVO ids and Data Sets Identifiers

[Francois Ochsenbein]

If I may intervene on this subject of the IVO identifiers, I would
strongly suggest not to use the hash symbol as a delimiter, because
it has a special meaning in the HTTP protocol: it indicates a marker
in the document, and what comes after the # symbol is quite generally
ignored by the HTTP servers.  For instance the output of an HTTP GET to
  http://www.stsci.edu/ftp/science/hdfsouth/warnings.html#NICMOS
is exactly identical to the output of
  http://www.stsci.edu/ftp/science/hdfsouth/warnings.html
(the browser simply scrolls the document to position it at the "NICMOS" marker)

Therefore in the general scheme of the IVO identification
   ivo://Authority.ID/(resource_key)(dataset/subset_identification)
the # sign could maybe appear in the 3rd part (dataset/subset_identification)
but certainly not a separator between the parts 2 and 3 (and moreover not
between the parts 1 and 2) if it is wished that a resource can be reached
using the http conventions.

In fact, for datasets I would more agree with Guenther's arguments:
one Authority.ID, and what follows it is defined under the responsability
of the Authority.ID who "publishes" the way to access to the data.
The dataset can effectively be a simple document like
   ivo://Authority.ID/Resource-Service/Repository/Intrument/datasetID

but could also be something like
   ivo://Authority.ID/RepositoryQuery?instrument=Intrument&ID=datasetID

As long as there is no ambiguity (the Authority.ID may "delegate" the
"naming space" to different missions or instruments or whatever) the
role of the identifiers is fulfilled. The problem with the links from
the journals is, as pointed out by Bob, the requirement for long-term
persistence which can only be achieved if any change in the curator is 
propagated to the Registry who has to make this mapping between the 
'permanent' and the 'actual' identifiers (the GLU was not bad in this role!)
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Francois Ochsenbein       ------       Observatoire Astronomique de Strasbourg
   11, rue de l'Universite F-67000 STRASBOURG       Phone: +33-(0)390 24 24 29
Email: francois at astro.u-strasbg.fr   (France)         Fax: +33-(0)390 24 24 17
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