Before revision: For every node N labelled by a problem or sub-problem P and for every method of the form P if P1 and … and Pn, there exists a set of children nodes N1, … , Nn of the node N, such that each node Ni is labelled by Pi.
After revision: For every node N labelled by a problem or sub-problem P and for every method of the form P if P1 and ... and Pn, there exists a set of children nodes N1, ... , Nn of the node N, such that each node Ni is labelled by Pi.