>Still, there are many cases where you want rules to fire in your UI before you submit it back to your business object. I really don't know what so say there. You can take the performance hit and call your business object with your dataset as a parameter. If the BO is on a remote machine this will serialize the dataset and send it over the network. One option would be to create a lightweight "business object" that lives client-side and handles the validation or anything that needs to be done before sending it back to the middle tier.
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>I really hope Mr. McNeish comes up with something good for this one.

Note to self: Actually, he already has. What I just described is the Emissary/Executant design pattern which is already in Mere Mortals for VFP. The documentation for that product is worth the price of the whole product alone!