>Your business tier is not in my application and my application delete a customer. ( or try to delete ).

I'm still not following. Is that a question? If you do not use business logic, then, of course, RI has to still be handled.


>>>He must receive a message from the data tier, ok ?

No, other way. The UI is where somebody has asked to delete a customer.

>Your business tier must receive a message about customer deleting .

From the UI.

>>>So who's handle it the data or the business tier ? :)

Every tier "handles" it. Just different aspects.

>But what I mean is that the data tiers receive the message first and communicate to the business tier after.

Again, AFAIK, that's exactly opposite.

>So even when the business tier handle the RI, the delete trigger is send by the data tier.

There isn't a brick wall between tiers or types of objects. The RULE for deleting or allowing orphaned invoices can be a business rule...but the back end can still use a delete trigger.

But, in your situation, what happens if your data source is XML?