On the existence of cutoffs for model checking disjunctive timed networks Luca Spalazzi and Francesco Spegni DII, Universit`a Politecnica delle Marche Abstract. Given a logical formula and a system described as the com- position of arbitrarily many copies of some process template, the param- eterized model checking problem wants to establish whether the system satisfies the formula. The focus is on the fact that the property should not depend on the actual number of participating processes. Exactly this, makes the problem equivalent to verifying an infinite state system, and thus undecidable problem in general. Several authors identified relevant sub-classes of systems or formulae to be model checked. In this work we study the parameterized model checking problem of real-time systems against real-time temporal logics. In particular we study the possibility of finding an upper bound to the size of the system, known as cutoff, ensuring that adding more partici- pants does not change the set of satisfiable formulae. A distinction exists between dynamic cutoffs, depending both on the process templates and the formula, and static cutoffs, that only consider the templates. We start by introducing disjunctive timed networks. We show they do not admit static cutoffs, in general. Then we identify a subfamily that admits static cutoff, implying that the parameterized model checking problem is decidable. 1 Motivations Many types of system are naturally described as the combination of several agents or processes cooperating in order to reach a common task (distributed algorithms, protocols, . . . ). When the number of participants is a parameter of the system, which is expected to behave correctly despite its exact value, we say that we are handling a parameterized system. The parameterized verification problem is the problem of checking whether a specification holds in a parameterized system, for any number of participants. This is known to be an undecidable problem in general, but there exists a variety of restrictions that isolate families of systems and properties whose parameter- ized model checking problem is decidable. In this work we focus on a specific subset of systems, viz. real-time systems where processes are finite state and communicate by means of transitions with disjunctive boolean guards referring to the neighbor locations . This family of systems, that we call disjunctive timed networks, is a combination of timed net- works by Abdulla et al. [2] and Emerson and Kahlon’s disjunctively guarded processes [11].