Jw Wieger Wesselink

Static Analysis Techniques for Parameterised Boolean Equation Systems

Parameterised Boolean Equation Systems (PBESs) can be used to encode and solve various types of model checking and equivalence checking problems. PBESs are typically solved by symbolic approximation or by instantiation to Boolean Equation Systems (BESs). The latter technique suffers from something similar to the state space explosion problem and we propose to tackle it by static analysis techniques, which we tailor for PBESs. We introduce a method to eliminate redundant parameters and a method to detect constant parameters. Both lead to a better performance of the instantiation and they can sometimes even reduce problems that are intractable due to the infinity of the underlying BES to tractable ones.

Realizability criteria for compositional MSC

Synthesizing a proper implementation for a scenario-based specification is often impossible, due to the distributed nature of implementations. To be able to detect problematic specifications, realizability criteria have been identified, such as non-local choice. In this work we develop a formal framework to study realizability of compositional MSC [GMP03]. We use it to derive a complete classification of criteria that is closely related to the criteria for MSC from [MGR05]. Comparing specifications and implementations is usually complicated, because different formalisms are used. We treat both of them in terms of a single formalism. Therefore we extend the partial order semantics of [Pra86, KL98] with a way to model deadlocks and with a more sophisticated way to address communication.

Incremental verification of owicki/gries proof outlines using PVS

Verifications of parallel programs are frequently based on automated state-space exploration techniques known as model checking. To avoid state-space explosion problems, theorem proving techniques can be used, for example by manually annotating programs with suitable assertions and using these assertions to prove their correctness (e.g. using the Owicki/Gries theory). We propose a method to support assertion-based methods with theorem provers like PVS. Emphasis is on the typical incremental character of assertion-based methods, and on automated strategies for proving correctness of the proof outlines.

Formal methods impact on ANSI standard HL7/IM - filling gaps in MSC theory

Health level seven (HL7) is an ANSI standard that provides a comprehensive framework for electronic health information. The most-widely used HL7 specification is called infrastructure management, which facilitates health-care applications to exchange key sets of clinical and administrative data. This paper results from a cooperation between the authors of the HL7 standard and academics who have actively participated in an HL7 technical committee. The challenge taken is to apply formal methods to a standard in creation, which can be incomplete and subject to change. Based on this contribution to HL7, we address some gaps in the current theory on message sequence chart with respect to deferred behavior and to non-local choice

Liveness analysis for parameterised Boolean equation systems

We present a sound static analysis technique for fighting the combinatorial explosion of parameterised Boolean equation systems (PBESs). These essentially are systems of mutually recursive fixed point equations ranging over first-order logic formulae. Our method detects parameters that are not live by analysing a control flow graph of a PBES, and it subsequently eliminates such parameters. We show that a naive approach to constructing a control flow graph, needed for the analysis, may suffer from an exponential blow-up, and we define an approximate analysis that avoids this problem. The effectiveness of our techniques is evaluated using a number of case studies.

Abstraction in Fixpoint Logic

We present a theory of abstraction for the framework of parameterised Boolean equation systems, a first-order fixpoint logic. Parameterised Boolean equation systems can be used to solve a variety of problems in verification. We study the capabilities of the abstraction theory by comparing it to an abstraction theory for Generalised Kripke modal Transition Systems (GTSs). We show that for model checking the modal μ-calculus, our abstractions can be exponentially more succinct than GTSs and our theory is as complete as the GTS framework for abstraction. Furthermore, we investigate the completeness of our theory irrespective of the encoded decision problem. We illustrate the potential of our theory through case studies using the first-order modal μ-calculus and a real-time extension thereof, conducted using a prototype implementation of a new syntactic transformation for parameterised Boolean equation systems.

EufDpll - A Tool to Check Satisfiability of Equality Logic Formulas

Decision procedures for subsets of First-Order Logic form the core of many verification tools. Applications include hardware and software verification. The logic of Equality with Uninterpreted Functions (EUF) is a decidable subset of First-Order Logic. The EUF logic and its extensions have been applied for proving equivalence between systems. We present a branch and bound decision procedure for EUF logic based on the generalisation of the Davis-Putnam-Loveland-Logemann procedure (EUF-DPLL). EufDpll is a tool to check satisfiability of EUF formulas based on this procedure.

Formalising the Dezyne Modelling Language in mCRL2

Dezyne is an industrial language with an associated set of tools, allowing users to model interface behaviours and implementations of reactive components and generate executable code from these. The tool and language succeed the successful ASD:Suite tool set, which, in addition to modelling reactive components, offers a set of verification capabilities allowing users to check the conformance of implementations to their interfaces. In this paper, we describe the Dezyne language and a model transformation to the mCRL2 language, providing users access to advanced model checking capabilities and refinement checks of the mCRL2 tool set.