inverse mapping multiple foreign keys?

[Tim Drury <td...@siliconmotorsports.com>]

I have an object that has two foreign keys and is held in a
List of one of its parent tables.  Here is the example:

(obviously this is pseudo code)

class Invoice {
	Contact shipper;
	Contact buyer;
	List shipperNotes;  // List of Note objects
	List buyerNotes;	  // List of Note objects
}

I cannot simply attach a Note object to an Invoice without
specifing whether the Note is owned by the shipper or buyer
Contact.  The DB table for Note is:

NOTE
----
ID INTEGER (PK)
NOTE VARCHAR(8192)
...
OWNERID INTEGER (FK to Contact table)
INVOICEID INTEGER (FK to Invoice table)

here is an excerpt from my repository.xml inside the Invoice def:

	<collection-descriptor
		name="buyerNotes"
		element-class-ref="model.Note"
		auto-update="true"
		auto-delete="true"
		orderby="TIMECREATED"
		sort="ASC"
		>
		<inverse-foreignkey field-ref="invoiceId"/>
<!--		<inverse-foreignkey field-ref="buyerId"/> -->
	</collection-descriptor>

I'm at a loss how to describe to OJB how it should fill the Note's
InvoiceId with the Id from the Invoice created _and_ the buyerId
with the Id from the Contact object of the buyer.  It would seem
the <inverse-foreignkey> tag would need two attributes, a field-ref
telling it the target field to fill and another attribute to tell
it the _source_ field.

I searched the email archives and came up empty.  Any ideas?  Should
I have designed the database schema differently?

Thanks,
-tim