“…However, if ¬ϕ = def ∃x ∈ R (reachable(x) ∧ ∧ ¬safe(x)) holds, then we cannot conclude that ∃x ∈ Z (reachable(x) ∧ ∧ ¬safe(x)) holds. Now, as indicated in the literature (see, for instance, [17,19,29,30,31]) the verification of infinite state reactive systems can be done via program specialization and, in particular, in [19] we proposed a technique consisting of the following two steps: (Step 1) the specialization of the constraint logic program that encodes the given system, with respect to the query that encodes the property to be verified, and (Step 2) the construction of the perfect model of the specialized program.…”