This is not an RI issue, it's more of a constraint issue. I do agree that a lot of the constraints can be implemented in the business tier (especially to minimize roundtrips) but that's a separate issue.

>>Can you give me an example of data that only pertains to itself and not to the business domain? IMHO, data is just an outcome or representation of, as you say "carrying out the business domain" and is pretty synonymous with each other.
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>Sure.
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>Example: Birthdate must be less than or equal to date of death. This is true for every data set regardless of the business domain.