This example describes a graph with nodes and edges. The operation newTarget creates a new link (edge) between a source node and exactly one new node. This operation uses the operation oclIsNew. The example corresponds to the section `Validating Pre- and Postconditions with USEŽ Graph.use: one class Node and one association Edge one operation newTarget with two postconditions Graph.cmd: three calls of newTarget both postconditions evaluate to true after the first call the first postcondition evaluates to false and the second to true after the second call and the first postcondition evaluates to true and the second to false after the last call