Karen:

I agree with Ed as well (once he corrected me on the topic at hand)--we 
have been existing for some time in a world that uses a lot of different 
identifiers, and I don't think we're in any better position than were to 
cut down on that, nor is there any real reason to do so.

I would point out that in your examples below (and in Ed's as far as I 
can tell) there's a bit of mushiness about whether one is identifying a 
resource or a description of a resource (a.k.a. metadata record).  
Interestingly, we've been pretty good in MARC about making the 
distinction clear (in different fields, for the most past), though in 
practice we've tended to muddy the waters a bit, given that LCCNs and 
OCLC numbers are far more ubiquitous than real resource identifiers 
(ISBNs, ISSNs, etc.).

We surely need both, and, as you say, we need to be really, really clear 
about what we're identifying.

Diane

Karen Coyle wrote:
> I agree with Ed that we aren't in a position to make statements about
> "best" identifiers at this point in time, and that the bottom line is
> that all identifiers for instances must be URIs.
>
> At the same time, I think that we need to scrutinize re-use of
> identifiers in the same way that we scrutinize the re-use of metadata
> elements. The rule for metadata elements is that use must be
> determined by the definition of the element, and we can use this same
> rule for identifiers. Some examples:
>
> ISBN: product number assigned by publisher.
> LCCN: number assigned by Library of Congress that identifies a
> metadata record in the LoC system.
> OCLC number: number assigned by OCLC that identifies a metadata record
> in the OCLC system.
> etc.
>
> We often re-use these numbers because they are handy hooks into
> metadata databases, but we should always use them with their original
> meaning intact. I'm all in favor of including all of these numbers in
> our metadata because they can be useful, but we shouldn't consider
> that any of them actually *identify* metadata that we create. They
> always identify what they are originally defined as identifying.
>
> kc
>
>
>
> On Tue, Nov 25, 2008 at 9:26 AM, Ed Summers <[log in to unmask]> wrote:
>   
>> On Mon, Nov 24, 2008 at 1:50 PM, Diane I. Hillmann <[log in to unmask]> wrote:
>>     
>>> The identifiers for the FRBR entities are coming--we're just waiting for an
>>> agreement within IFLA on the domain name, and they'll be added to the NSDL
>>> Registry--with luck by the end of the year.
>>>       
>> I think Rob was talking about identifiers for actual *instances* of
>> FRBR Entities, not about identifiers for classes and whatnot in the
>> FRBR vocabulary.
>>
>> My personal opinion is that RDA should follow in the footsteps of RDF
>> and allow any sort of URI to be used to identify a bibliographic
>> resource. One could well imagine RDA users wating to use ISBN URNs,
>> natural keys expressed as URLs, info-uris, DOIs and Handles expressed
>> as URIs, etc. It seems premature to restrict the types of identifiers
>> that oould be used other than requiring them to be URIs.
>>
>> //Ed
>>
>>     
>
>
>
>