I've been watching all this discussion about creating a "group id" for a
set of ISBNs, and I'm wondering if I'm missing something.

Since the collection of ISBNs can be treated as an equivalence class,
can't any arbitrary member of the class be designated as the group
identifier?  This eliminates the need to create a synthetic id, and it
means that, for singular items, there's no need to create a separate
group id.

In fact, assuming that a library has a single item, that ISBN is
designated as the "group id" for the group of one thing.  Then, when the
library acquires a second item that should be part of the group, it
should be easy to update the equivalence class.

- David

Hickey,Thom wrote:
> Right now there isn't a stable identifier for the clusters in xISBN.
> OCLC-PICA is looking into how OCLC could supply that to help local
> catalogs group there items, though.
> --Th
> -----Original Message-----
> From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of
> Ben Ostrowsky
> Sent: Tuesday, May 23, 2006 8:54 AM
> To: [log in to unmask]
> Subject: Re: [CODE4LIB] Musings on using xISBN in our Horizon catalog
> I appreciate all the comments thus far and I hope my chiming in again
> won't shut anybody up.
> I'll see if there's a cheap way to query the live database, as Mike
> Rylander suggests.
> If not, I'm thinking about how to be sure I don't have duplicate work
> IDs.  Here's the scenario:
> 1. We query xISBN for a particular book and get a set of related ISBNs.
> 2. We check the catalog and derive a set of related ISBNs in our
> catalog.
> 3. We cache this derived set by assigning an auto-incrementing sequence
> number to that set and linking it to each member of the derived set.
> 4. A new edition of the same work becomes available.  We add it to our
> catalog.  When we query the local xISBN server, it finds no matching
> records.  So we query xISBN and get the set consisting of all the old
> ISBNs plus the ISBN of the new edition.
> 5. We check this new result set against the catalog and cache the result
> by assigning an auto-incrementing sequence number.
> 6. Someone looks up one of the old editions.
> 7. We query the local cache and find... What?  Duplicate ISBNs that we
> have to de-dupe on the fly each time?  Inelegant, to be sure.
> That's why I'd love to know whether the xISBN database uses a common
> identifier for each set of ISBNs, and whether (and I know 'pretty
> please' is a poor justification for changing an API) it might be exposed
> for this reason.
> Am I making an invalid assumption here?  Or might there be a way to
> tweak the algorithm so that we don't run into this problem?
> Ben

David J. Fiander
Digital Services Librarian