[OAI-implementers] Identifiers [was: Re: OAI-PMH + IEEE LTSC LOM]

[Chris Hubick]

On Wed, 2004-03-10 at 22:52, Hussein Suleman wrote:
> for not exactly LOM, but the IMS metadata set (LOM + minor 
> modifications) ... check the CSTC archive with baseURL
>    http://www.cstc.org/cgi-bin/OAI/CSTC.pl

Hi again :)

This, and an email Kat Hagedorn sent me off list (hi Kat), reminds me of
a big question about identifiers...

As you may know, LOM identifiers are catalog/entry *pairs*.  That is to
say, the entry is namespaced by it's catalog - the repository could
conceivably have two different records with the same identifier entry in
different catalogs.  However, OAI and Dublin Core, and RSS, etc, use a
*single* string as an identifier.

In a repository that harvests from a number of different systems through
a variety of protocols, and has identifiers from many catalog types (not
necessarily URI's)...

How does one map an arbitrary catalog/entry *pair*, to a *single*
identifier string?

My answer was to use a URN:

'urn:' + <catalog> + ':' + <entry>

Note:
1) Identifiers used in OAI messages must be URI's.
2) In the OAI Identifier format ('oai:'), the namespace ID must be a
domain name.  The repository Hussein linked violates this.
3) The LOM/RDF stuff seems to expect all people to use 'URI' as a
catalog in their LOM data (?).

My runner up was a Universal Name:
'{' + <catalog> + '}' + <entry>
That notation was invented by James Clark
http://www.jclark.com/xml/xmlns.htm ), but the URI req killed that idea.
Ideally, the LOM to Dublin Core mapping in Appendix B of the IEEE LTSC
LOM spec would have set up a practice this, but alas, it does not.

Has anyone else tackled this problem?

Thanks.

-- 
Chris Hubick
mailto:chrish@athabascau.ca
mailto:chris@hubick.com
phone:1-780-421-2533 (work)
phone:1-780-721-9932 (cell)
http://www.hubick.com/


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