VizieR repository

  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   Therefore, the status can still be 'active' while the   item is obsolete.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.

-- 
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   /  ~   /, Sebastien Derriere   mailto:derriere-at-astro.u-strasbg.fr
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