Applying Formal Methods to Gossiping Networks with mCRL and Groove

In this paper we explore the practical possibilities of using formal methods to analyze gossiping networks. In particular, we use mCRL and Groove to model the peer sampling service, and analyze it through a series of model transformations to CTMCs and finally MRMs. Our tools compute the expected value of various network quality indicators, such as average path lengths, over all possible system runs. Both transient and steady state analysis are supported. We compare our results with the simulation and emulation results found in [10]

Bug Hunting with False Negatives Revisited

Safe data abstractions are widely used for verification purposes. Positive verification results can be transferred from the abstract to the concrete system. When a property is violated in the abstract system, one still has to check whether a concrete violation scenario exists. However, even when the violation scenario is not reproducible in the concrete system (a false negative), it may still contain information on possible sources of bugs. Here, we propose a bug hunting framework based on abstract violation scenarios. We first extract a violation pattern from one abstract violation scenario. The violation pattern represents multiple abstract violation scenarios, increasing the chance that a corresponding concrete violation exists. Then, we look for a concrete violation that corresponds to the violation pattern by using constraint solving techniques. Finally, we define the class of counterexamples that we can handle and argue correctness of the proposed framework. Our method combines two formal techniques, model checking and constraint solving. Through an analysis of contracting and precise abstractions, we are able to integrate overapproximation by abstraction with concrete counterexample generation

A prover for the mu mu CRL toolset with applications : version 0.1

This document describes an automated theorem prover, based on an extension of binary decision diagrams. The prover transforms quantifier-free formulae into equivalent BDD-forms, w.r.t.~to some algebraic data specification. The prover is used by four tools for the symbolic analysis of distributed systems specified in $mu$CRL (i.e.~process algebra plus algebraic data types). The main techniques are invariants and confluence. Two case studies are reported: the DKR leader election protocol [13], and SPLICE [15], a coordination architecture of industrial origin. In both cases using confluence information leads to a reduced state space

Operational semantics of rewriting with priorities

AbstractWe study the semantics of term rewriting systems with rule priorities (PRS), as introduced in Baeten et al. (1989). Three open problems posed in that paper are solved, by giving counter examples. Moreover, a class of executable PRSs is identified. A translation of PRSs into transition system specifications (TSS) is given. This translation introduces negative premises. We prove that the translation preserves the operational semantics

A BDD-representation for the logic of equality and uninterpreted functions (a full version with proofs).

The logic of equality and uninterpreted functions (EUF) has been proposed for processor verification. This paper presents a new data structure called Binary Decision Diagrams for representing EUF formulas (EUF-BDDs). We define EUF-BDDs similar to BDDs, but we allow equalities between terms as labels instead of Boolean variables. We provide an approach to build a reduced ordered EUF-BDD (EUF-ROBDD) and prove that every path to a leaf is satisfiable by construction. Moreover, EUF-ROBDDs are logically equivalent representations of EUF-formulae, so they can also be used to represent state spaces in symbolic model checking with dat

A rewriting approach to binary decision diagrams

AbstractBinary decision diagrams (BDDs) provide an established technique for propositional formula manipulation. In this paper, we present the basic BDD theory by means of standard rewriting techniques. Since a BDD is a DAG instead of a tree we need a notion of shared rewriting and develop appropriate theory. A rewriting system is presented by which canonical reduced ordered BDDs (ROBDDs) can be obtained and for which uniqueness of ROBDD representation is proved. Next, an alternative rewriting system is presented, suitable for actually computing ROBDDs from formulas. For this rewriting system a layerwise strategy is defined, and it is proved that when replacing the classical apply-algorithm by layerwise rewriting, roughly the same complexity bound is reached as in the classical algorithm. Moreover, a layerwise innermost strategy is defined and it is proved that the full classical algorithm for computing ROBDDs can be replaced by layerwise innermost rewriting without essentially affecting the complexity. Finally a lazy strategy is proposed sometimes performing much better than the traditional algorithm