We describe a method for reducing the complexity of temporal logic model checking in systems composed of many parallel processes. The goal is to check properties of the components of a system and then deduce global properties from these local properties. The main difficulty with this type of approach is that local properties are often not preserved at the global level. We present a general framework for using additional interface processes to model the environment for a component. These interface processes are typically much simpler than the full environment of the component. By composing a component with its interface processes and then checking properties of this composition, we can guarantee that these properties will be preserved at the global level. We give two example compositional systems based on the logic CTL*.

We give a comprehensive and unifying survey of the theoretical aspects of Temporal and modal logic.

The role of automatic formal protocol verification in hardware design is considered. Principles are identified that maximize the benefits of protocol verification while minimizing the labor and computation required. A new protocol description language and verifier (both called Mur') are described, along with experiences in applying them to two industrial protocols that were developed as part of hardware designs.

A fundamental difficulty in automatic formal verification of finite-state systems is the state explosion problem -- even relatively simple systems can produce very large state spaces, causing great difficulties for methods that rely on explicit state enumeration. We address the problem by exploiting structural symmetries in the description of the system to be verified. We make symmetries easy to detect by introducing a new data type scalarset, a finite and unordered set, to our description language. The operations on scalarsets are restricted so that states are guaranteed to have the same future behaviors, up to permutation of the elements of the scalarsets. Using the symmetries implied by scalarsets, a verifier can automatically generate a reduced state space, on the fly. We provide a proof of the soundness of the new symmetry-based verification algorithm based on a definition of the formal semantics of a simple description language with scalarsets. The algorithm has been implemented ...

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.

We demonstrate the feasibility of using the XSB tabled logic programming system as a programmable fixed-point engine for implementing efficient local model checkers. In particular, we present XMC, an XSBbased local model checker for a CCS-like value-passing language and the alternation-free fragment of the modal mu-calculus. XMC is written in under 200 lines of XSB code, which constitute a declarative specification of CCS and the modal mu-calculus at the level of semantic equations. In order to gauge the performance of XMC as an algorithmic model checker, we conducted a series of benchmarking experiments designed to compare the performance of XMC with the local model checkers implemented in C/C++ in the Concurrency Factory and SPIN specification and verification environments. After applying certain newly developed logic-programmingbased optimizations (along with some standard ones), XMC's performance became extremely competitive with that of the Factory and shows promise in its comparison with SPIN.

Symbolic trajectory evaluation provides a means to formally verify properties of a sequential system by a modified form of symbolic simulation. The desired system properties are expressed in a notation combining Boolean expressions and the temporal logic "next-time" operator. In its simplest form, each property is expressed as an assertion [A =) C], where the antecedent A expresses some assumed conditions on the system state over a bounded time period, and the consequent C expresses conditions that should result. A generalization allows simple invariants to be established and proven automatically. The verifier operates on system models in which the state space is ordered by "information content". By suitable restrictions to the specification notation, we guarantee that for every trajectory formula, there is a unique weakest state trajectory that satisfies it. Therefore, we can verify an assertion [A =) C] by simulating the system over the weakest trajectory for A and testing...

Traditional ROBDD-based methods of automated verification suffer from the drawback that they require a binary representation of the circuit. To overcome this limitation we propose a broader class of decision graphs, called Multiway Decision Graphs (MDGs), of which ROBDDs are a special case. With MDGs, a data value is represented by a single variable of abstract type, rather than by 32 or 64 boolean variables, and a data operation is represented by an uninterpreted function symbol. MDGs are thus much more compact than ROBDDs, and this greatly increases the range of circuits that can be verified. We give algorithms for MDG manipulation, and for implicit state enumeration using MDGs. We have implemented an MDG package and provide experimental results.

) 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...

Thanks to a variety of new techniques, state-space exploration is becoming an increasingly effective method for the verification of concurrent programs. One of these techniques, hashing without collision detection, was proposed by Holzmann as a waytovastly reduce the amount of memory needed to store the explored state space. Unfortunately, this reduction in memory use comes at the price of a high probability of ignoring part of the state space and hence of missing existing errors. In this paper, we carefully analyze this method and show that, by using a modified strategy, it is possible to reduce the risk of error to a negligible amount while maintaining the memory use advantage of Holzmann's technique. Our proposed strategy has been implemented and we describe experiments that confirm the excellent expected results.