You can do an empty query in their catalog, and use the "Original 
Location" facet to filter to a holding library. Programatically, I'm not 
sure, but you'd probably need to use the Hathi files: 
http://www.hathitrust.org/hathifiles.

-Jon

On 08/03/2012 11:07 AM, Eric Lease Morgan wrote:
> If I needed/wanted to know what materials held by my library were also in the HaitTrust, then programmatically how could I figure this out? In other words, do you know of a way to query the HaitTrust and limit the results to items my library owns? --Eric Lease Morgan