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Parameterised Boolean Equation Systems
 In Theoretical Computer Science
, 2004
"... Boolean equation system are a useful tool for verifying formulas from modal mucalculus on transition systems (see [18] for an excellent treatment). We are interested in an extension of boolean equation systems with data. This allows to formulate and prove a substantially wider range of properties ..."
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Cited by 21 (9 self)
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Boolean equation system are a useful tool for verifying formulas from modal mucalculus on transition systems (see [18] for an excellent treatment). We are interested in an extension of boolean equation systems with data. This allows to formulate and prove a substantially wider range of properties on much larger and even infinite state systems. In previous works [11, 15] it has been outlined how to transform a modal formula and a process, both containing data, to a socalled parameterised boolean equation system, or equation system for short. In this article we focus on techniques to solve such equation systems.
Equivalence checking for infinite systems using parameterized boolean equation systems
 In Proc. CONCUR’07, LNCS 4703
, 2007
"... Abstract. In this paper, we provide a transformation from the branching bisimulation problem for infinite, concurrent, dataintensive systems in linear process format, into solving Parameterized Boolean Equation Systems. We prove correctness and illustrate the approach with two examples. We also pro ..."
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Cited by 15 (9 self)
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Abstract. In this paper, we provide a transformation from the branching bisimulation problem for infinite, concurrent, dataintensive systems in linear process format, into solving Parameterized Boolean Equation Systems. We prove correctness and illustrate the approach with two examples. We also provide small adaptations to obtain similar transformations for strong and weak bisimulations and simulation equivalences. 1
Efficient TemporalLogic Query Checking for Presburger Systems
, 2005
"... This paper develops a framework for solving temporallogic querychecking problems for a class of infinitestate system models that compute with integervalued variables (socalled Presburger systems, in which Presburger formulas are used to define system behavior). The temporallogic querychecking ..."
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Cited by 3 (1 self)
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This paper develops a framework for solving temporallogic querychecking problems for a class of infinitestate system models that compute with integervalued variables (socalled Presburger systems, in which Presburger formulas are used to define system behavior). The temporallogic querychecking problem may be formulated as follows: given a model and a temporal logic formula with placeholders, compute a set of assignments of formulas to placeholders such that the resulting temporal formula is satisfied by the given model. Temporallogic query checking has proved useful as a means for requirements and design understanding; existing work, however, has focused only on propositional temporal logic and finitestate systems. Our method is based on a symbolic modelchecking technique that relies on proof search. The paper first introduces this modelchecking approach and then shows how it can be adapted to solving the temporal queries in which formulas may contain integer variables. We also present experimental results showing the computational efficacy of our approach.
2010 13th IEEE International Symposium on Object/Component/ServiceOriented RealTime Distributed Computing Workshops Towards a Modelbased Refinement Process for Contractual State Machines
"... Abstract—We present a rigorous modelbased approach to the stepwise design of contractual state machines, which are a simplified form of statecharts extended with declarative specifications. The approach is based on application of a set of refinement patterns, that can be validated against a formal ..."
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Abstract—We present a rigorous modelbased approach to the stepwise design of contractual state machines, which are a simplified form of statecharts extended with declarative specifications. The approach is based on application of a set of refinement patterns, that can be validated against a formal semantics, and that are implemented using updateinplace model transformations. We describe the integrated tool support we are implementing for this modelbased approach, and illustrate the approach with small examples. I.
Project: Verification of Complex Hierarchical Systems (VOCHS) Principal Investigator: dr.ir. T.A.C. Willemse Funding Organisation: NWO (2010–2014)
"... experiments in the Large Hadron Collider in Geneva. The software, controlling this experiment, consists of 20,000 finite state machines, which are strictly hierarchically organised. The complexity of the software has grown out of hand and it is not predictable anymore. This is becoming a nuisance. C ..."
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experiments in the Large Hadron Collider in Geneva. The software, controlling this experiment, consists of 20,000 finite state machines, which are strictly hierarchically organised. The complexity of the software has grown out of hand and it is not predictable anymore. This is becoming a nuisance. Consequently, the CMS research group currently invests in the verification thereof by translating the finite state machines to mCRL2, which is a behavioural specification and analysis methodolgy which we have developed. Verification of small constellations of state machines is quite straightforward. However, the verification of the entire system consisting of 20,000 parallel components is of a different category, which cannot be done by CERN alone, but requires our skill and experience. We are convinced that the hierarchical architecture enables us to prove the correctness of this massive control system. As the Large Hadron Collider will become fully operational in the coming years, an urge is felt to get the software right. In tackling this problem, we pursue two main approaches concurrently. The first approach is to employ (symbolic) PBES technology that we have developed for the verification of modal properties. Our second approach is to employ the sheer power of parallel processing using (distributed clusters of) multicore cpus for solving BESs resulting from modularised PBESs. This project is geared towards the verification challenge at CERN; its underlying purpose is to increase the verification capabilities as a whole.
3. Principle investigator: dr.ir. T.A.C. Willemse.
"... Model checking is a popular technique for verifying the designs of reallife systems, including realtime systems, hybrid systems, probabilistic systems and datadependent systems. Unfortunately, the results underlying the techniques from such specialised areas can be hard to translate to other area ..."
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Model checking is a popular technique for verifying the designs of reallife systems, including realtime systems, hybrid systems, probabilistic systems and datadependent systems. Unfortunately, the results underlying the techniques from such specialised areas can be hard to translate to other areas because they rely on particular models. Moreover, systems cannot be classified as e.g. strictly realtime or strictly datadependent: in many cases, a system is in the intersection of various classes. While properties can be verified in their separate domains using dedicated techniques, verifying the behaviour in the intersection of various domains is often impossible with the currently available techniques. We propose to address these issues by studying the existing approaches in one framework: Parameterised Boolean Equation Systems (PBESs). Work by Mateescu, Groote and Mateescu, and Groote and Willemse has shown that the model checking problem for datadependent systems can be translated to solving PBESs. We propose to extend these results to realtime systems, and embed results from these specialist areas in the PBESs approach. Apart from the advantages that are brought about by studying known results in a single framework, PBESs offer a novel, and sometimes unique view on the model checking problem. For instance, Groote and Willemse showed that certain verification problems can be transformed to easier problems, simply by determining the syntactic form of the PBES and looking up its solution. While such techniques are commonplace in mathematics (e.g. for differentiation of functions), they are unique to the field of model checking and deserve further investigations.
Project Description
"... Software engineers increasingly employ heterogeneous notations for specifying complex software systems, which mix declarativelogic and operational specification styles. This is because requirements are frequently stated in restricted forms of natural language or simple spreadsheets (declarative) a ..."
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Software engineers increasingly employ heterogeneous notations for specifying complex software systems, which mix declarativelogic and operational specification styles. This is because requirements are frequently stated in restricted forms of natural language or simple spreadsheets (declarative) and combined with design elements in the form of component interfaces (declarative, also operational) or state machines (operational). The popular Unified Modeling Language (UML) supports such heterogeneous notations, e.g., with its class diagrams, its state machine variant and its Object Constraint Language (OCL) [67]. A recent academic focus wrt. heterogeneity is on modelling formalisms for reactive systems software, including hierarchical state machines and protocol interface theories. For example, Contractual State Machines [33] uses logic constraints to express contracts between a reactive system and its environment and between the system’s components, and employs patterns that allow designers to systematically refactor and refine components. Another example are Modal Interfaces [61] where a system component may be required to implement several interfaces simultaneously, i.e., to satisfy their conjunction. One concrete application example where such heterogenous modelling formalisms are useful is the development of mode logics in aircraft control systems. Mode logics monitor an aircraft’s
Data Structure Choices for OntheFly Model Checking of RealTime Systems
"... Abstract—This paper studies the performance of sparsematrixbased data structures to represent clock zones (convex sets of clock values) in an onthefly predicate equation system model checker for timed automata. We analyze the impact of replacing the dense difference bound matrix (DBM) with both ..."
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Abstract—This paper studies the performance of sparsematrixbased data structures to represent clock zones (convex sets of clock values) in an onthefly predicate equation system model checker for timed automata. We analyze the impact of replacing the dense difference bound matrix (DBM) with both the linkedlist CRDZone and arraylist CRDArray data structure. From analysis on the pairedexamplebyexample differences in time performance, we infer the DBM is either competitive with or slightly faster than the CRDZone, and both perform faster than the CRDArray. Using similar analysis on space performance, we infer the CRDZone takes the least space, and the DBM takes less space than the CRDArray. I.