>>I think what Nancy is saying is that RI should be enforced by the biz rules. I agree. However, where that is implemented is what we are debating here. There are valid reasons for doing this with biz objects or letting the data store do it. Either way, it is biz rules that determine how it is done.
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>I write this in this discussion
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>>RI preserves relationships between tables when records are entered or deleted, it's not a business rule.
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>>But RI is only a part of the DATA Integrity.
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>>So confusion is comming when some business rules will enforced data rules to hold the DATA Integrity.
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>>But remember n tier is only a responsability layout and the business tiers is a two face layer ( one for Data and one for the User )
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>>So the DATA tier is able to communicate with other tier. ( to ask and receive informations )
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>>But the DATA Integrity is the reponsability of the data tier ( no way out of this !) also when enforced by business rules.
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>Don't you agree ?

Business rules are business rules. You can...and will enforce them at different levels. Saying that a US phone number will always be formatted as (nnn) nnn-nnnn is a business rule..and one that will be enforced by the UI. Saying how you allow deletes/edits/adds to a particular table is RI. Where you enforce that really depends on the implementation. You can just as easily put it in the data objects, or have the actual data store handle it.