Thanks John. If you can reference any works, please post them.

>Well lets see......
>
>Specific cites...I am sure I can come up with a few, but I wont at this juncture... Rather, lets use some common sense...shall we....
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>The data services tier is concerned with two basic operations:
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>1. Fetching Data
>2. Updating data - which includes inserts, updates, and deletes
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>Now, if one believes that RI is inextricably bound to the act of updating a database, it is clear that the RI rules belong in the data services tier.
>
>Rules like - not selling to folks that have A/R over 120 days, or you cannot book an order for a customer on credit hold all belong in the business services layer. Rules like this can change over time. The rules can become more stringent, or they can be relaxed. These are classic middle tier rules
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>A rule such as not booking an order for a non-existent customer belongs in the data services tier. Prior to letting updates go through, you need to know if an orphaned record will result, etc. These type of rules belong in the data services tier....
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>However....
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>I have only stated where the rules belong. There is nothing that says the business tier could not query the data services tier to determine if an R/I rule will fail. The two are contractually obligated to one another. More specifically, the business tier is contractually obligated to do whatever the data-services tier tells it do. If the data services tier says an update should not occur, the updates should not occur, regardless of what the status of the business rules.
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>My argument is somewhat baited here... Notice that I said where the rules belong, not necessarily who should invoke the rules... In other words, I see nothing wrong with the biz tier invoking the RI rules hosted in the data services tier. In any case, the RI rules *belong* in the data services tier.