>I understand that for Nancy Folsom the Referentiel integrity tier is the business tiers.
>
>I simply try to demonstrate it is not .

Except for arcane exercise or technologies I've not seen, I say Marcel's "RI is Data tier" is the most feasable.

RI is most appropriately a responsibility of the Data tier. And it's useful to ask "who's business is it anyway?" when talking about the Business tier. Just as the term "interface" manifests differently when paired with differing nouns (consider an ADO interface vs. a User interface) so also does "business". For example, I'm sitting in my office right now "doing business." But later when I take a walk down the hallway, "doing business" means something else entirely. ;-)

While RI can be seen to have "business" concerns to take care of, it's Data tier business, not User business concerns. "RI" is made of nouns. It's responsibility is the relational integrity of the data, just as a table structure contributes to a table's integrity. To say RI is a business tier concern (even if it's technically possible) then allows tables stuctures to become business tier as well. What good is this? And why stop there - what about PKs? NULL capability? Identity?

Business tier is concerned with User business: bounce this check, lucky one-millionth customer, did we spam Mr. Bennett today? and so on...

Uh...I was gonna think up something else but I've got some "business" to take care of down the hallway...

Later, Steven-