  It is easy to regard a set of nodes as the analog of a Cauchy surface, e.g., the set {a, b, c}, and it is obvious if arbitrary data are put on those nodes the data will generate a unique solution in the  future.[2]  If the value of the field at node a is 3 and at node b is 7, then its value at node d will be 3Wad and its value at node e will be 3Wae + 7Wbe. By varying the weighting factors we can adjust the dynamics, but in an acyclic graph the future evolution of the field will always be unique.