Hi Matt,

> please confirm that it is valid/reasonable to let a user enter a string into a lookup box that matches a string-based PO# or JobNo reference, like "MS3424C" or "UR-23423A" and then I have to do an intermediate lookup to search for the corresponding Integer PK.

A business object absolutely can have methods that take a non-PK identifier. You don't even have to translate this to an integer PK for the query, as long as your links are done on the PK. Simplified:

PROCEDURE GetCustomerByCustomerNo(tcCustNo)
  SELECT ... ;
    FROM Customers ;
   JOIN Addresses ON Customer.pk == Addresses.CustFK ;
   WHERE CustNo = tcCustNo
ENDPROC

Key point is that these values should never make it from the WHERE clause into the JOIN clause.