>>RI is purely a function of relationships between entities in a database.. not the validity of the data held within the columns of non-RI columns.
>
>I disagree. Here is a biz rule that expresses referential integrity.
>
>"When a salesman is fired, move all of his customers to his manager". This prevents orphan customer records. This rule may change over time... such as
>"When a salesman is fired, move all of his customers to the newest salesperson".

Hi Evan,

I don't agree. RI is simply a state the data is in at this moment. The example is a business rule. It states what has to happen in a certain business situation. A by-product of the rule is what the data structure looks like so you can maintain RI and enforce the business rule.

What happens when the client says, "When a salesperson is fired, don't do anything with customer, just delete the salesperson". Your'e screwed if the customer table has a FK to the salesperson table. The moment a salesperson is deleted, you have an orphaned key.

In that situation you should add a link table between saleperson and customer. Now you can delete either at will without busting RI.