Have you seen the VuFind ILS driver spec? This might answer your question (or at least prove to be a useful reference):
Apologies if I'm misunderstanding your question -- please let me know if you still need more information.
From: Andrews, Mark J. [mailto:mark.j.andrews@...]
Sent: Tuesday, January 26, 2010 1:49 PM
Subject: [VuFind-Tech] Gettings holdings for a list of id's
When VuFind asks the upstream ILS for piece-level holdings by id, how are the id's separated?
Mark A. @ Creighton U.
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