Distributed Branching Bisimulation Reduction of State Spaces

AbstractEnumerative model checking tools are limited by the size of the state space to which they can be applied. Reduction modulo branching bisimulation usually results in a much smaller state space and therefore enables model checking of much larger state spaces. We present an algorithm for reducing state spaces modulo branching bisimulation which is suitable for distributed implementation. The target architecture is a cluster with a high bandwidth interconnect. The algorithm is based on partition refinement and it works on transition systems which contain cycles of invisible steps, without eliminating strongly connected components first. To avoid fine grained parallelism, the algorithm refines the whole partition instead of just a single block in the partition. We prove correctness and also present some experimental results obtained with single threaded and distributed prototypes

On Lossless Compression of 1-bit Audio Signals

In this paper we consider the problem of lossless compression of 1-bit audio signals. We study the properties of some existing proposed solutions. We also discuss possible improvements. Other methods have been considered, and the results are reported

Refinement of Kripke Models for Dynamics

We propose a property-preserving refinement/abstraction theory for Kripke Modal Labelled Transition Systems incorporating not only state mapping but also label and proposition lumping, in order to have a compact but informative abstraction. We develop a 3-valued version of Public Announcement Logic (PAL) which has a dynamic operator that changes the model in the spirit of public broadcasting. We prove that the refinement relation on static models assures us to safely reason about any dynamic properties in terms of PAL-formulas on the abstraction of a model. The theory is in particular interesting and applicable for an epistemic setting as the example of the Muddy Children puzzle shows, especially in the view of the growing interest for epistemic modelling and (automatic) verification of communication protocols

Distributed Branching Bisimulation Minimization by Inductive Signatures

We present a new distributed algorithm for state space minimization modulo branching bisimulation. Like its predecessor it uses signatures for refinement, but the refinement process and the signatures have been optimized to exploit the fact that the input graph contains no tau-loops. The optimization in the refinement process is meant to reduce both the number of iterations needed and the memory requirements. In the former case we cannot prove that there is an improvement, but our experiments show that in many cases the number of iterations is smaller. In the latter case, we can prove that the worst case memory use of the new algorithm is linear in the size of the state space, whereas the old algorithm has a quadratic upper bound. The paper includes a proof of correctness of the new algorithm and the results of a number of experiments that compare the performance of the old and the new algorithms

Distributing requirements specifications on basic splice

This is an extension of work presented in [Jaco van de Pol-Expressiveness of Basic Splice. Report SEN-R0033, December 2000]. It is proved that the seemingly weak architecture Basic Splice introduced there --in which the coordination of processes is done using only a global set with read/write primitives-- can support a distributed implementation of a large class of requirements specifications, namely LPEs (a muCRL intermediate representation of specifications)

Epistemic Verification of Anonymity

Anonymity is not a trace-based property, therefore traditional model checkers are not directly able to express it and verify it. However, by using epistemic logic (logic of knowledge) to model the protocols, anonymity becomes an easily verifiable epistemic formula. We propose using Dynamic Epistemic Logic to model security protocols and properties, in particular anonymity properties. We have built tool support for DEL verification which reuses state-of-the-art tool support for automata-based verification. We illustrate this approach by analyzing an anonymous broadcast protocol and an electronic voting protocol. By comparison with a process-based analysis of the same protocols, we also discuss the relative (dis)advantages of the process-based and epistemic-based verification methods in general