Assume Client A wants to sell a package to client B.
How should I write down a smart contract that prevents from B to receive the package while being refuse to pay in a claim that he isn't receive anything? (B is cheating)
In another word, How can I link with the action of a real(physical) transfer of item\package, and digital transfer of money? (Does it must rely on a physical sensor of the delivery?)
A good contract reference/solutions would be appreciated.