Tim A. C. Willemse

Test generation based on symbolic specifications

Classical state-oriented testing approaches are based on simple machine models such as Labelled Transition Systems (LTSs), in which data is represented by concrete values. To implement these theories, data types which have infinite universes have to be cut down to finite variants, which are subsequently enumerated to fit in the model. This leads to an explosion of the state space. Moreover, exploiting the syntactical and/or semantical information of the involved data types is non-trivial after enumeration. To overcome these problems, we lift the family of testing relations ioco

An overview of the mCRL2 toolset and its recent advances

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Guidelines for a graduate curriculum on embedded software and systems

to the level of Symbolic Transition Systems (STSs). We present an algorithm based on STSs, which generates and executes tests on-the-fly on a given system. It is sound and complete for the ioco

Parameterised Boolean Equation Systems

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Instantiation for Parameterised Boolean Equation Systems

testing relations.

Heuristics for ioco-based test-based modelling

The analysis of complex distributed systems requires dedicated software tools. The mCRL language and toolset have been developed to support such analysis. We highlight changes and improvements made to the toolset in recent years. On the one hand, these affect the scope of application, which has been broadened with extended support for data structures like infinite sets and functions. On the other hand, considerable progress has been made regarding the performance of our tools for state space generation and model checking, due to improvements in symbolic reduction techniques and due to a shift towards parity game-based solving. We also discuss the software architecture of the toolset, which was well suited to accommodate the above changes, and we address a number of case studies to illustrate the approach.

Formalising and analysing the control software of the Compact Muon Solenoid Experiment at the Large Hadron Collider

The design of embedded real-time systems requires skills from multiple specific disciplines, including, but not limited to, control, computer science, and electronics. This often involves experts from differing backgrounds, who do not recognize that they address similar, if not identical, issues from complementary angles. Design methodologies are lacking in rigor and discipline so that demonstrating correctness of an embedded design, if at all possible, is a very expensive proposition that may delay significantly the introduction of a critical product. While the economic importance of embedded systems is widely acknowledged, academia has not paid enough attention to the education of a community of high-quality embedded system designers, an obvious difficulty being the need of interdisciplinarity in a period where specialization has been the target of most education systems. This paper presents the reflections that took place in the European Network of Excellence Artist leading us to propose principles and structured contents for building curricula on embedded software and systems.

Consistent correlations for parameterised Boolean equation systems with applications in correctness proofs for manipulations

Boolean equation system are a useful tool for verifying formulas from modal mu-calculus on transition systems (see [9] 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 [4,6] it has been outlined how to transform a modal formula and a process, both containing data, to a so-called parameterised boolean equation system, or equation system for short. In this article we focus on techniques to solve such equation systems. We introduce a new equivalence between equation systems, because existing equivalences are not compositional. We present techniques similar to Gaus elimination as outlined in [9] that allow to solve each equation system provided a single equation can be solved. We give several techniques for solving single equations, such as approximation (known), patterns (new) and invariants (new). Finally, we provide several small but illustrative examples of verifications of modal mu-calculus formulas on concrete processes to show the use of the techniques.

Experiences in developing the mCRL2 toolset

Verification problems for finite- and infinite-state processes, like model checking and equivalence checking, can effectively be encoded in Parameterised Boolean Equation Systems (PBESs). Solving the PBES solves the encoded problem. The decidability of solving a PBES depends on the data sorts that occur in the PBES. We describe a manipulation for transforming a given PBES to a simpler PBES that may admit solution methods that are not applicable to the original one. Depending on whether the data sorts occurring in the PBES are finite or countable, the resulting PBES can be a Boolean Equation System (BES) or an Infinite Boolean Equation System (IBES). Computing the solution to a BES is decidable. Computing the global solution to an IBES is still undecidable, but for partial solutions (which suffices for e.g.local model checking), effective tooling is possible. We give examples that illustrate the efficacy of our techniques.

Verification of reactive systems via instantiation of Parameterised Boolean Equation Systems

Model-based conformance testing provides a mathematically sound technique to assess the quality of systems and check the correctness of a system with respect to a model. Most systems, however, are built or modified without documenting the (new) specifications, thereby limiting the use of model-based testing techniques. In this paper, we describe a method to obtain models automatically from an existing system, using model-based testing techniques relying on ioco-based testing. These models are useful for e.g. regression testing, or for the testing of different configurations of systems. We illustrate the effectiveness of our approach using a case-study in which we test mutants of the system against models that have been automatically extracted from the (correct) system.