“…This problem, dual of verification, attempts not to prove that the system M is correct under all inputs u ∈ U , but simply to find a faulty execution w = M(u), without any formal guarantees that it will be found. The most effective technique, as illustrated in [2,34], turns the falsification problem into the following optimization problem: "minimize ρ(φ, w) subject to w = M(u), u ∈ U ." The robustness value ρ is expected to be continuous in u, and by definition is w ̸ |= φ when ρ(φ, w) < 0.…”