I originally thought it belonged in the data tier, but I've recently been convinced otherwise.

RI is a business rule because without it in the database, the database is still valid (i.e. it's not corrupted), but whether it makes sense to leave invoices behind after deleting their customer is a business rule. And that is what RI is.

>Any other comments on this? I have always thought of RI as being a data tier issue but here is a quote from the Foxwiki