On Thu, 13 Mar 2003, Phil Barker wrote:

> 1.1.1 Catalog (re Andy's comments)
> Any chance of someone like JISC setting up a Handle registry? Does it come
> within the scope of the JISC call 5/03
> (http://www.jisc.ac.uk/index.cfm?name=funding_5_03)

That is certainly worth thinking about... but I don't think it falls under
the scope of that particular call (which is primarily targetted at getting
'publishers' to adopt some of the technologies specified in the IE
technical architecture).

Again, I think it is worth thinking about the functional requirement
here...

So, in the context of X4L (but assuming that any X4L requirement is likely
to be a requirement more generally) do we want to be able to:

1) assign unique, persistent identifiers to learning objects (and parts
thereof)

2) resolve the identifier (i.e. enter the identifier or a modified form of
the identifier into our browser 'Address' bars and be directed) to the
current location of the object

or both of these?

I'm going to assume that the requirement is for both.  Shout if it isn't!

OK.  I'm going to suggest that DOIs, Handles and PURLs would all meet both
requirements.  Of these, DOIs and Handles have the slight advantage that
they are not tied to the HTTP protocol and that they are underpinned by a
properly distributed database technology).

Any form of URI other than 'http', 'ftp', etc. would only meet
requirement 2 if we could develop an associated 'resolver' service.

In the OAI world, requirement 1) has been met by the use of 'oai' URIs to
identify each 'item' in OAI repositories.  An example URI is

  oai:rdn.ac.uk:12345-67890

The 'oai' part says this is an 'oai' URI, i.e. it conforms to the 'oai'
URI scheme. The 'rdn.ac.uk' bit says that this URI was assigned by the
RDN.  The '12345-67890' part is an identifier that is unique within the
RDN.  Overall, uniqueness is guaranteed (as long as the 'rdn.ac.uk' part
is unique - which is why the use of DNS domains for this part is strongly
encouraged).

At the moment, there is no 'resolver' service for 'oai' URIs.  If I type
'oai:rdn.ac.uk:12345-67890' into my browser Address bar I'll get an error
- because my browser doesn't understand the 'oai' URI scheme.

One could build a resolver service for these URIs by harvesting metadata
records from all known OAI repositories and building a list of all 'oai'
URIs and their associated URLs (possibly taken from the metadata record
for that item). As far as I know, no-one has done this yet - but it would
be quite a neat idea.  Then one would need a technology for actually
doing the resolution.  It would be possible to use either the Handle
system or the PURL system for this.

For example, one could register all the 'oai' URIs with the PURL resolver
at

http://purl.org/

using a convention like

http://purl.org/oai/oai:rdn.ac.uk:12345-67890

This would be pretty trivial to do.  Doing so would allow people to
actually use the 'oai' URIs to link to things.

Doing something similar with the handle system would, I think, be fairly
straight-forward.

OK, so here's my suggestion.  We find an existing URI scheme (or if
absolutely necessary invent our own one) that, like the 'oai' scheme,
allows us to idependently assign unique identifiers to learning objects.
We then build a resolver service for those URIs using the PURL or Handle
systems.  (Initially, we would not actually run a copy of the PURL or
Handle resolver software locally in the UK - but longer term we could
think about doing that if performance issues deemed it necessary).

If we could assume that all learning object repositories were going to
expose their metadata using the OAI-PMH, then we could do this by using
the 'oai' URI scheme.  That would be my preferred approach.

Clearly, even without the need to run our own resolver, there is still a
need to register the 'oai' URIs that we assign with the PURL resolver -
this would have to be undertaken centrally, based on regular OAI
harvesting.  Therefore this would have to be a funded 'service'.
Therefore someone would have to make a proposal to JISC (or whoever) to
run this service.

The advantage of this approach is that, assuming that we can agree to it
in principle, we can start assigning 'oai' identifiers now, without
waiting for the resolver to be deployed.  I.e. we meet requirement 1) in
the short term and requirement 2) in the medium term?

Comments?

Andy
--
Distributed Systems, UKOLN, University of Bath, Bath, BA2 7AY, UK
http://www.ukoln.ac.uk/ukoln/staff/a.powell       +44 1225 383933
Resource Discovery Network http://www.rdn.ac.uk/