I don't know if this is possible, but if it is, I haven't been able wrap what I know of NHibernate around it.

I have two tables. The first has a collection of objects from the second, but the second references the first by two columns that are not the primary key of the first table.

How the heck (if at all) do you map that?

Illustration:

Table for Obj A has columns Aid, number, string
Table for Obj B has columns Bid, number, string

A has a one-to-many relationship with B based on number and string

EDIT: B does not have to have a reference back to A in the mapping