Hi everyone,
May I suggest taking a look at the "Document" pattern in "Business Modeling
with UML" by Eriksson and Penker (OMG/Wiley 2000) or as it was originally
described in "Data Model Patterns: Conventions of Thought" by Hay (Dorset
House 1996).
This pattern defines the abstract models (in UML naturally!) for materials
that can be copied, distributed and versioned, and may help with thinking
about this problem...
- Scott
On 1/5/03 5:34 pm, "Lorna M. Campbell" <[log in to unmask]> wrote:
> Hi Phil,
>
>> But what if the creator uploads the object to two repositories which
>> assign two different identifiers? Nothing wrong with that, until a
>> third repository (or resolving service, or cross searching portal)
>> gets hold of [metadata for] both copies and needs to work out whether
>> they are duplicates [and it will need to work out whether what it has
>> are two different metadata records for one resource, or duplicate
>> metadata records].
>
> I totally agree with your comments about multiple ids and duplicate and
> multiple records. This is digital rights management and appropriate
> copy territory and I'm afraid I have no easy answers, surprise, surprise.
>
> I have also heard arguments that every instance of an object and every
> instance of a record should indeed have a unique id as they are unique
> instances of the object or record, and that the relation fields, should
> be used to indicate the relation between the multiple objects and/or
> records. However using and maintaining the relations fields is a bit of
> a nightmare so I'm not convinced by this idea. I need to give this a
> lot more thought......
>
>> There will be ways round this problem, but I think that it would still
>> be best to avoid unecessarily multiplicity of object ids. So I would
>> suggest that ids need to be allocated as early as possible (ie during
>> the creation or the initial publishing of the object) and repositories
>> which receive an object with an existing id should not create a new
>> id--or (more realistically) if the repository does create a new id, it
>> should keep it to itself.
>
> I absolutely agree that repositories should maintain the ids they
> receive, or hide any additional ids they create, as you say. How do you
> suggest these ids are "allocated" in the first place though? If for
> example, a developer uses the new Reload tool to package a learning
> object and add metadata to it prior to uploading it to a repository how
> will they "allocate" the id?
>
> And of course there's also the interopability issue of how the
> repository then deals with the id. Incidentally I liked Ben's idea of
> investigating the transfer of identifiers between repositories at the
> CodeBash2. I'll get that on the agenda.
>
> Bye
> Lorna
>
>>
>>
>>
>>
>> Phil
>>
>>
>
> --
> 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/
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