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

Andy Powell a.powell@ukoln.ac.uk
Thu, 11 Mar 2004 23:58:03 +0000 (GMT Standard Time)

On Thu, 11 Mar 2004, Chris Hubick wrote:

> 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>

One problem with this approach is that there is presumably very little
consistency across services in the way that 'catalog' is assigned - i.e.
the 'catalog' is not taken from a controlled vocabulary.  So although you
end up with a single single string identifier (the URN) you don't really
have a mechanism for reliably comparing URNs from different sources.

It seems to me that the 'catalog'/'entry' pairing in LOM is a bit broken
- because it really requires a global registry of 'catalog' names to work
properly.  (At least, without a global registry I can have no way of
knowing if your 'catalog' is the same as my 'catalog').  URIs already
provide a global space within which new identifier schemes can be created
- why not use it, rather than building a LOM-specific registry.

In partricular, the proposed 'info' URI scheme


provides an open mechanisn for assigning URIs to information assets that
have identifiers in public namespaces but have no representation within
URI space.

> Has anyone else tackled this problem?

Not really, but you might be interested in

Guidelines for encoding identifiers in Dublin Core and IEEE LOM metadata

which basically suggests that URIs should *always* be used.

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