>Is a Candidate Key a form of Business Rule? Are Referential Integrity rules a form of Business Rules?

>I would appreciate advice on whether to enforce the uniqueness of key fields or expressions in a 3 (or more) tier structure in the data services or the business services layer. Similarly, should Referential Integrity be maintained in the data services or business services layer?

There was a good dicussion of this see

"Referential integrity which tier?" Thread #288250 Message #288250 on 1999/11/07