The reason its an exploit is based on the games dynamics. (using the italy example above) Italy 100 gold for science 9 of which come from us. NOw we cancel the deal...well like when you are in the diplo screen you cant change your science rate..so now They only have 91 gold for sceince BUT they slider doesnt adjust so it says 20gpt available.after you cancel the resource deal and then you can re-up it for 20. Now here is the kicker...the deals all have to be cancel adn redone in the same diplo session. If you exit out...the AI can adjust their slider. SO my proposal is if you cancel a deal during 1 turn you cant make another deal till the next turn. If the gold is still available...then the AI wants to trade it, if its not there...they preferred to use it elsewhere. No one wants to take that chance because in all the games where I tested this...the gold was not there. You read the threads on this...and everything is done in the same session...no one ever exits. That is taking advantage of the game mechanics and therefore its an exploit.