1. A computer-readable medium having encoded thereon software for supply chain activity optimization involving multiple enterprises at a buyer computer system, the computer-readable medium comprising instructions for: access a forecasted demand for at least one item; automatically and without user input subsequent to accessing the forecasted demand, generate one or more proposed flexible trade contracts using the forecasted demand for the item; automatically and without user input subsequent to generating the proposed flexible trade contracts, communicate each proposed flexible trade contract to a seller computer system to initiate an automatic collaborative negotiation over the proposed flexible trade contract with the seller computer system; automatically and without user input subsequent to communicating the proposed flexible trade contract, as part of the automatic collaborative negotiation, receive at least one modification of the proposed flexible trade contract from the seller computer system for automatic evaluation and possible acceptance in response to communicating the proposed flexible trade contract; automatically and without user input subsequent to receiving the modification of the proposed flexible trade contract from the seller computer system, as part of the automatic collaborative negotiation, evaluate the modification to determine whether the modification is acceptable; automatically and without user input subsequent to evaluating the modification of the proposed flexible trade contract, as part of the automatic collaborative negotiation, accept the modification if the modification is acceptable; subsequent to execution of a flexible trade contract created based on the proposed flexible trade contract as a result of the automatic collaborative negotiation, take one or more actions to perform under the executed flexible trade contract; and subsequent to execution of the flexible trade contract created based on the proposed flexible trade contract as a result of the automatic collaborative negotiation, taking one or more actions to enforce the executed flexible trade contract.