No abstract

No abstract

Dickson's Lemma is a simple yet powerful tool widely used in decidability proofs, especially when dealing with counters or related data structures in algorithmics, verification and model-checking, constraint solving, logic, etc. While Dickson's Lemma is well-known, most computer scientists are not aware of the complexity upper bounds that are entailed by its use. This is mainly because, on this issue, the existing literature is not very accessible.We propose a new analysis of the length of bad sequences over (N k , ≤), improving on earlier results and providing upper bounds that are essentially tight. This analysis is complemented by a "user guide" explaining through practical examples how to easily derive complexity upper bounds from Dickson's Lemma.

Abstract. Symbolic model checking provides partially effective verification procedures that can handle systems with an infinite state space. So-called "acceleration techniques" enhance the convergence of fixpoint computations by computing the transitive closure of some transitions. In this paper we develop a new framework for symbolic model checking with accelerations. We also propose and analyze new symbolic algorithms using accelerations to compute reachability sets.

We investigate NLTL, a linear-time temporal logic with forgettable past. NLTL can be exponentially more succinct than LTL + Past (which in turn can be more succinct than LTL). We study satisfiability and model checking for NLTL and provide optimal automata-theoretic algorithms for these EXPSPACE-complete problems.

International audienceIn this paper, we study model checking of timed automata (TAs), and more precisely we aim at finding efficient model checking for subclasses of TAs. For this, we consider model checking TCTL and TCTL, over TAs with one clock or two clocks.\par First we show that the reachability problem is NLOGSPACE-complete for one clock TAs (i.e. as complex as reachability in classical graphs) and we give a polynomial time algorithm for model checking TCTL, over this class of TAs. Secondly we show that model checking becomes PSPACE-complete for full TCTL over one clock TAs. We also show that model checking CTL (without any timing constraint) over two clock TAs is PSPACE-complete and that reachability is NP-hard

Abstract. We prove that coverability and termination are not primitive-recursive for lossy counter machines and for Reset Petri nets.

No abstract