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Hi Andy, Thanks for clarifying this issue. As I've said before, I'm on really shaky ground when it comes to advising on identifiers :-} so I'd be really, really grateful if you would be willing to write up a proposal for "learning object identifiers". We could then incorporate your proposal into the next draft of the UKCMF. Thanks again. All the best Lorna Andy Powell wrote: >On Thu, 13 Mar 2003, Andy Powell wrote: > > > >>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 >> >> > >Many apologies, but having read this back to myself (and checked with the >OAI-PMH spec) I realise that what I said here is incorrect - and I'd >better correct myself before someone else does it for me :-). > >In the OAI-PMH, the 'oai' URI is used to identify an 'item'. An 'item' is >'a constituent of a repository from which metadata about a resource can be >disseminated'. So, what this means is that, in the contaxt of a learning >object repository (like, say, Jorum): > >- the learning object is the 'resource' >- the set of possible metadata descriptions about the resource (dc, ims, > etc.) is the 'item' >- each specific description (dc or ims or ...) is a 'record' > >The 'oai' URI scheme is used to identify the 'item' not the 'resource'. > >See > > http://www.openarchives.org/ > >for details. > >The rest of my argument still stands I think, namely that we should use >some form of URI to identify learning objects and that we should use the >PURL or Handle systems to resolve those URIs. > >So, the question is, what form of URI should we use given that we can't >use the 'oai' scheme (for resources)? > >Looking thru the list of registered schemes at IANA, I don't see anything >obvious, other than the 'urn', but I'm not convinced we should bother with >URNs for various reasons. Looking thru the list of unregistered schemes >at > > http://www.w3.org/Addressing/schemes > >I also don't see much of interest. That leaves us having to invent our >own scheme. One possibility would be to invent a learning object 'lo' >scheme (with a view to registering it in the longer term). > >If so, I'd suggest following the layout of the 'oai' scheme, i.e. > >lo:DNSdomain:identifer_within_domain > >e.g. > >lo:bath.ac.uk:12345-67890 > >Another possibility would be to simply use PURLs, adopting a similar >format, e.g. > >http://purl.org/lo/bath.ac.uk/12345-67890 > >PURLs of this form have the advantage of being able to be independently >assigned by learning object creators (because of the DNS domain part) and >they can easily be mapped to URIs of the form > >lo:bath.ac.uk:12345-67890 > >if necessary in the future, and to 'oai' URIs fo the form > >oai:bath.ac.uk:12345-67890 > >I.e., we could maintain a simple relationship between the learning object >'resource' PURLs and the corresponding OAI 'item' URIs. > >I have a strrong dislike of inventing our own URI scheme, so my gut >feeling is to use PURLs but I would really appreciate other's views on >this! > >Hope this all makes some sense! If it would help, I could write this up >as a firm proposal for 'learning object identifiers'? > >Andy. > > > >>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/ >> >> >> > >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/ > >. > > > -- Lorna M. Campbell Assistant Director Centre for Educational Technology Interoperability Standards (CETIS) Centre for Academic Practice, University of Strathclyde +44 (0)141 548 3072 http://www.cetis.ac.uk/