1. A method for communicating between a first element and a second: element in a system, the method comprising: determining at least one goal related to a task to be performed by the second element; determining at least one constraint related to how the at least one goal is to be achieved; communicating the at least one goal and the at least one constraint to the second element; and receiving an error message if the second element is not capable of achieving the at least one goal in accord with the at least one constraint.