code: public void link(Object obj, ObjectReferenceDescriptor ord, boolean insert)
      {
         linkOrUnlink(true, obj, ord, insert);
      }
docs: This method concatenate the main object and the specified reference
  object (1:1 reference a referenced object, 1:n and m:n reference a
  collection of referenced objects) by hand. This method is needed when
  in the reference metadata definitions the auto-xxx setting was disabled.
  More info see OJB doc.
  
  @param obj Object with reference
  @param ord the ObjectReferenceDescriptor of the reference
  @param insert flag signals insert operation