We can tuck any logical expressions in CHECK constraints, but all foreign keys are currently capable of right now is to verify that one or more column values are equal. In many cases it would be very useful to have foreign keys use more complex logical expressions. Also in some cases the ability to create constraints on indexed views would ...

Suppose that you need to enforce the following business rule: contracts cannot be changed after you have started working on them (let us assume that that particular business operates in the perfect world).  You can use a ROWVERSION column, a persisted computed one, and a foreign key constraint to implement this rule, and I ...