VizieR repository

[Sebastien Derriere]

  Dear harvesters :)

  I have opened a preliminary OAI-PMH interface to harvest the contents
of VizieR at the following address:

http://vizier.u-strasbg.fr/cgi-bin/registry/vizier/oai.pl

  You can test it with the OAI explorer, for example:
http://oai.dlib.vt.edu/cgi-bin/Explorer/oai2.0/testoai

  The repository handles two metadataPrefixes:
- the standard oai_dc for basic Dublin Core
- ivo_vr for metadata formatted in the VOResource-v0.9 schema

  I have adopted the following conventions. Your comments on these are
welcome:

* The AuthorityID has been set to "CDS". Is this the correct choice, or
should it look more like a domain name? Or should there be different
 AuthorityIDs for VizieR, Simbad, Aladin, ... etc in the case of CDS ???

* I have defined as 'Sets' the top-level categories in VizieR, and
the items correspond to the different 'Tables'. Should the items be
'Catalogues' rather than 'Tables'? (there are approx. 4000 catalogues,
and 10,000 tables - 1 cat. can contain several tables).
  Is there a way to handle different levels of granularity (sets,
subsets)?

* I still had problems with the allowed syntax for ResourceKey,
therefore I currently use a modified version of VOResource-v0.9.xsd
with the following:
   <xs:simpleType name="ResourceKeyType">
     <xs:restriction base="xs:string">
       <xs:pattern
value="[\w\d\-_\.!~\*'\(\)\+]+(/[\w\d\-_\.!~\*'\(\)\+]+)*"/>
     </xs:restriction>
   </xs:simpleType>

  This is to allow for the '+' char in the ResourceKey, as we have for
example
in VizieR tables from A&A coded as J/A+A/...
  In the IVOA Identifiers v0.2, the '+' was not forbidden, but the
RegExpr
in VOResource-v0.9.xsd didn't allow fot it.

* How do we deal with obsolete items in a registry?

  Sometimes, an item becomes obsolete in a repository,
  but it is very rare that it is acually deleted.
  Therefore, the status can still be 'active' while the
  item is obsolete.

  For example, the first 2MASS release is still active
  in VizieR (because there have been published papers
  referring to objects therein, and it is useful to have
  the original data available), but there is a flag to
  indicate that use of this catalogue is now deprecated
  because is it made obsolete by the new 2MASS catalogue.

  Maybe we should intrduce a new value for 'RelationshipType'
  in the VOResourceRelType schema, that would be 'deprecated-by'
  to indicate the link between the obsolete item and the new item
  that makes the other one obsolete.

* Not all the possible metadata are filled yet. At least the
required ones are. How are we supposed to describe the coverage
in this kind of OAI-PHM XML ? Should it be a second element in
the <metadata> section, formatted accordingly to the coverage
schema?

* Last question for now, how do we deal with mirrors/clones?
Should we copy this repository on all vizier clones, so that people 
can harvest on any vizier site?

Sebastien.
-- 
    _______
   /  ~   /, Sebastien Derriere   mailto:derriere at astro.u-strasbg.fr
  / ~~~~ //  Observatoire de Strasbourg    Phone +33 (0) 390 242 444
 /______//   11, rue de l'universite     Telefax +33 (0) 390 242 417
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