Is there a document that explains the database tables for Webcenter Enterprise Capture?

Hi, we use the invoice processing solution with WFR. Users complain that they don't know where their invoices have gone once they have hit commit on a scanned document. So we are designing a report that will help the users keep track on their invoices. This is fine for WFR but for WEC, we don't know where to look in the database structure. We also unsure when entries are made in the tables. Is at the point the batch is created or when it is committed? I can't find any documentation on this. Any help with this would be appreciated.