If you put a - in front of the filter, that will exclude a value... so &filter[]=-format:ebook should work.  The tricky part is figuring out how to fit something into the UI to make this happen.

- Demian

From: Karla Smith [smith@winnefox.org]
Sent: Friday, July 26, 2013 6:28 PM
To: 'vufind-general@lists.sourceforge.net'
Subject: [VuFind-General] Excluding facets

Is there a way to have VuFind limit based on excluding a facet? Like, show me all the harry potter stuff that ISN’T an e-book or e-audio. 
Has anyone tried that? I suppose it would be complicated to get it to work both ways—exclude and include.
Maybe for future VuFind development?
Just an end of the week stray thought, as I prep to do some VuFind training at our site…
Karla Smith, ILS Manager
Winnefox Library System
Oshkosh,WI 54901