Structural Analysis of Boolean Equation Systems

We analyse the problem of solving Boolean equation systems through the use of structure graphs. The latter are obtained through an elegant set of Plotkin-style deduction rules. Our main contribution is that we show that equation systems with bisimilar structure graphs have the same solution. We show that our work conservatively extends earlier work, conducted by Keiren and Willemse, in which dependency graphs were used to analyse a subclass of Boolean equation systems, viz., equation systems in standard recursive form. We illustrate our approach by a small example, demonstrating the effect of simplifying an equation system through minimisation of its structure graph

Verification of safety requirements for program code using data abstraction

Large systems in modern development consist of many concurrent processes. To prove safety properties formal modelling techniques are needed. When source code is the only available documentation for deriving the system's behaviour, it is a difficult task to create a suitable model. Implementations of a system usually describe behaviour in too much detail for a formal verification. Therefore automated methods are needed that directly abstract from the implementation, but maintain enough information for a formal system analysis. This paper describes and illustrates a method by which systems with a high degree of parallelism can be verified. The method consists of creating an over-approximation of the behaviour by abstracting from the values of program variables. The derived model, consisting of interface calls between processes, is checked for various safety properties with the mCRL2 tool set

Verification of safety requirements for program code using data abstraction

Large systems in modern development consist of many concurrent processes. To prove safety properties formal modelling techniques are needed. When source code is the only available documentation for deriving the system's behaviour, it is a difficult task to create a suitable model. Implementations of a system usually describe behaviour in too much detail for a formal verification. Therefore automated methods are needed that directly abstract from the implementation, but maintain enough information for a formal system analysis. This paper describes and illustrates a method by which systems with a high degree of parallelism can be verified. The method consists of creating an over-approximation of the behaviour by abstracting from the values of program variables. The derived model, consisting of interface calls between processes, is checked for various safety properties with the mCRL2 tool set

Conversion of LSAT behavioral specifications to automata

The Logistics Specification and Analysis Tool (LSAT) is a model-based engineering tool used for manufacturing system design and analysis. Using a domain specific language, a system can be specified in LSAT. In this paper, a conversion method is presented to obtain the system behavior of an LSAT specification in automata structure.Comment: 10 pages, 6 figure

Relaxed Operational Semantics of Concurrent Programming Languages

We propose a novel, operational framework to formally describe the semantics of concurrent programs running within the context of a relaxed memory model. Our framework features a "temporary store" where the memory operations issued by the threads are recorded, in program order. A memory model then specifies the conditions under which a pending operation from this sequence is allowed to be globally performed, possibly out of order. The memory model also involves a "write grain," accounting for architectures where a thread may read a write that is not yet globally visible. Our formal model is supported by a software simulator, allowing us to run litmus tests in our semantics.Comment: In Proceedings EXPRESS/SOS 2012, arXiv:1208.244

Efficiently enforcing mutual state exclusion requirements in symbolic supervisor synthesis

Given a model of an uncontrolled system and a requirement specification, a supervisory controller can be synthesized so that the system under control adheres to the requirements. There are several ways in which informal behavioral safety requirements can be formalized, one of which is using mutual state exclusion requirements. In current implementations of the supervisor synthesis algorithm, synthesis may be inefficient when mutual state exclusion requirements are used. We propose a method to efficiently enforce these requirements in supervisor synthesis. We consider symbolic supervisor synthesis, where Binary Decision Diagrams are used to represent the system. The efficiency of the proposed method is evaluated by means of an industrial and academic case study

Semantics and expressiveness of ordered SOS

AbstractStructured Operational Semantics (SOS) is a popular method for defining semantics by means of transition rules. An important feature of SOS rules is negative premises, which are crucial in the definitions of such phenomena as priority mechanisms and time-outs. However, the inclusion of negative premises in SOS rules also introduces doubts as to the preferred meaning of SOS specifications.Orderings on SOS rules were proposed by Phillips and Ulidowski as an alternative to negative premises. Apart from the definition of the semantics of positive GSOS rules with orderings, the meaning of more general types of SOS rules with orderings has not been studied hitherto. This paper presents several candidates for the meaning of general SOS rules with orderings and discusses their conformance to our intuition for such rules.We take two general frameworks (rule formats) for SOS with negative premises and SOS with orderings, and present semantics-preserving translations between them with respect to our preferred notion of semantics. Thanks to our semantics-preserving translation, we take existing congruence meta-results for strong bisimilarity from the setting of SOS with negative premises into the setting of SOS with orderings. We further compare the expressiveness of rule formats for SOS with orderings and SOS with negative premises. The paper contains also many examples that illustrate the benefits of SOS with orderings and the properties of the presented definitions of meaning