>>Reasons for it being in the biz tier:
>
>>- domain expert may make relational integrity statements like "if a sales person is fired, move all of their customers to his boss". Clearly this is a business rule.

>This is not referential integrity.
>This is the contained level ( The level of the information in the data container ) this relation is not a data referentiel relation but a contained information relation the relation is done with any key. Nothing to do with referential integrity

Not sure if I completely follow, could you elobrate?

The definition of referential intergrity is "The rules governing data consistency, specifically the relationships between the primary keys and foreign keys of different tables."

Is this exactly what the customer has expressed, but at a more abstract level?