Abstract not found

The research on algorithmic verification methods for concurrent and parallel systems has mostly focussed on finite-state systems, with applications in e.g. communication protocols and hardware systems. For infinite-state systems, e.g. systems that operate on data from unbounded domains, algorithmic verification is more difficult, since most verification problems are in general undecidable. In this paper, we consider the verification of a particular class of infinite-state systems, namely systems consisting of finite-state processes that communicate via unbounded lossy FIFO channels. This class is able to model e.g. link protocols such as the Alternating Bit Protocol and HDLC. The unboundedness of the channels makes these systems infinite-state. For this class of systems, we show that several interesting verification problems are decidable by giving algorithms for verifying the following classes of properties.

Well-structured transition systems (WSTS's) are a general class of infinite state systems for which decidability results rely on the existence of a well-quasi-ordering between states that is compatible with the transitions. In this article, we provide an extensive treatment of the WSTS idea and show several new results. Our improved definitions allow many examples of classical systems to be seen as instances of WSTS's.

) Parosh Aziz Abdulla Uppsala University K¯arlis Cer¯ans University of Latvia Bengt Jonsson Uppsala University Yih-Kuen Tsay National Taiwan University Abstract Over the last few years there has been an increasing research effort directed towards the automatic verification of infinite state systems. For different classes of such systems (e.g., hybrid automata, data-independent systems, relational automata, Petri nets, and lossy channel systems) this research has resulted in numerous highly nontrivial algorithms. As the interest in this area increases, it will be important to extract common principles that underly these and related results. This paper is concerned with identifying general mathematical structures which could serve as sufficient conditions for achieving decidability. We present decidability results for systems which consist of a finite control part operating on an infinite data domain. The data domain is equipped with a well-ordered and well-founded preorder such tha...

. We consider symbolic on-the-fly verification methods for systems of finite-state machines that communicate by exchanging messages via unbounded and lossy FIFO queues. We propose a novel representation formalism, called simple regular expressions (SREs), for representing sets of states of protocols with lossy FIFO channels. We show that the class of languages representable by SREs is exactly the class of downward closed languages that arise in the analysis of such protocols. We give methods for (i) computing inclusion between SREs, (ii) an SRE representing the set of states reachable by executing a single transition in a system, and (iii) an SRE representing the set of states reachable by an arbitrary number of executions of a control loop of a program. All these operations are rather simple and can be carried out in polynomial time. With these techniques, one can construct a semi-algorithm which explores the set of reachable states of a protocol, in order to check variou...

Recently well-quasi orders in general, and homeomorphic embedding in particular, have gained popularity to ensure the termination of program analysis, specialisation and transformation techniques. In this paper,

We consider the verification of a particular class of infinite-state systems, namely systems consisting of finite-state processes that communicate via unbounded lossy FIFO channels. This class is able to model e.g. link protocols such as the Alternating Bit Protocol and HDLC. In an earlier paper, we showed that the problems of checking reachability, safety properties, and eventuality properties are decidable for this class of systems. In this paper, we show that the following problems are undecidable, namely ffl The model checking problem in propositional temporal logics such as Propositional Linear Time Temporal Logic (PTL) and Computation Tree Logic (CTL). ffl The problem of deciding eventuality properties with fair channels: do all computations eventually reach a given set of states if the unreliable channels satisfy fairness assumptions. The results are obtained through a reduction from a variant of Post's Correspondence Problem. This research report is a revised and extended ...

Program specialisation aims at improving the overall performance of programs by performing source to source transformations. A common approach within functional and logic programming, known respectively as partial evaluation and partial deduction, is to exploit partial knowledge about the input. It is achieved through a well-automated application of parts of the Burstall-Darlington unfold/fold transformation framework. The main challenge in developing systems is to design automatic control that ensures correctness, efficiency, and termination. This survey and tutorial presents the main developments in controlling partial deduction over the past 10 years and analyses their respective merits and shortcomings. It ends with an assessment of current achievements and sketches some remaining research challenges.

Abstract. We illustrate the use of logic programming techniques for finite model checking of CTL formulae. We present a technique for infinite state model checking of safety properties based upon logic program specialisation and analysis techniques. The power of the approach is illustrated on several examples. For that, the efficient tools logen and ecce are used. We discuss how this approach has to be extended to handle more complicated infinite state systems and to handle arbitrary CTL formulae. 1

Over the past few years increasing research effort has been directed towards the automatic verification of infinite-state systems. This paper is concerned with identifying general mathematical structures which can serve as sufficient conditions for achieving decidability. We present decidability results for a class of systems (called well-structured systems) which consist of a finite control part operating on an infinite data domain. The results assume that the data domain is equipped with a preorder which is a well quasi-ordering, such that the transition relation is ``monotonic' ' (a simulation) with respect to the preorder. We show that the following properties are decidable for well-structured systems: v Reachability: whether a certain set of control states is reachable. Other safety properties can be reduced to the reachability problem. 1