Thanks, Jörg.

One very quick point:

> Do not rely on ISBN as a unique
> identifier.
-- Just to be absolutely clear, we're not trying to use an ISBN as an identifier.  Indeed, relating Instances that use the same ISBN is not even in our view at present (and may never be, for all the reasons given about ISBNs to date).  Likewise, there are no plans to relate Works that have Instances that share ISBNs.  But, if we have a MARC record with three different ISBNs in it, as a general rule, we are making the assumption that each represents a distinct Instance of the Work being described (in our records there are often two ISBNs - one for the hard cover and the other for the paper back).  Now, the calculus will change if we can reasonably determine we are dealing with a MARC record that describes a multi-volume Work, for example.  The three ISBNs could mean something different in such a scenario.

*Per MARC record*, ISBNs offer a guide to splitting said MARC record into a BIBFRAME Work and one or more BIBFRAME Instances.


> -----Original Message-----
> From: Bibliographic Framework Transition Initiative Forum
> [mailto:[log in to unmask]] On Behalf Of Jörg Prante
> Sent: Friday, May 17, 2013 9:19 AM
> To: [log in to unmask]
> Subject: Re: [BIBFRAME] What's an instance?
> Kevin,
> yes, I can run an analysis over a snapshot of our union catalog
> comprising of around 4.847.212 ISBNs. It will take some time to write
> the code.
> Due to the official policy of the ISBN agencies, the reuse was strictly
> forbidden - but the ISBN number pool is segmented into countries and
> their publishers, which take charge over the number use. There is no
> technical mechanism to enforce correct use or to grant or revoke ISBNs
> by a third party. Beside applying the same ISBN to different editions,
> there are other cases. Some publishers wanted to save resources and
> simply broke the ISBN rules when they ran out of money (or they were
> rejected from receiving more ISBN numbers). They started to recycle
> ISBNs of books they had out of print for many years, hoping no one will
> ever notice. Or, publishers did not properly file their ISBN pool usage.
> For example, when publishers took over other publisher's business and
> their ISBN pools, there was no safe way of verifying what ISBNs were
> already taken or not. ISBN was in active use as primary identifiers in
> ISBN registers for no longer than 5 or 10 years. It's giving us
> headaches for a very long time. Do not rely on ISBN as a unique
> identifier.
> Jörg
> Am 16.05.13 23:54, schrieb Ford, Kevin:
> >   Is there any way to quantify, for example, how often publishers
> actually reuse ISBNs in different editions (is that even tecnically
> permitted?)?