Renegotiating
Renegotiating happens when a performer discovers in the process of executing a task that the requirements were not in fact clearly specified or that the deadline is no longer achievable. In order to enter renegotiation, a performer must notify the customer, after which they both re-enter planning for the task in question.
If a performer no longer expects to complete a task by the deadline, or is no longer sure what completion means, they MUST enter renegotiation - this is what keeps the system in sync with reality.
Next, see viewing.