A Graph-Based Semantics Workbench for Concurrent Asynchronous Programs

A number of novel programming languages and libraries have been proposed that offer simpler-to-use models of concurrency than threads. It is challenging, however, to devise execution models that successfully realise their abstractions without forfeiting performance or introducing unintended behaviours. This is exemplified by SCOOP---a concurrent object-oriented message-passing language---which has seen multiple semantics proposed and implemented over its evolution. We propose a "semantics workbench" with fully and semi-automatic tools for SCOOP, that can be used to analyse and compare programs with respect to different execution models. We demonstrate its use in checking the consistency of semantics by applying it to a set of representative programs, and highlighting a deadlock-related discrepancy between the principal execution models of the language. Our workbench is based on a modular and parameterisable graph transformation semantics implemented in the GROOVE tool. We discuss how graph transformations are leveraged to atomically model intricate language abstractions, and how the visual yet algebraic nature of the model can be used to ascertain soundness.Comment: Accepted for publication in the proceedings of FASE 2016 (to appear

Decentralised Evaluation of Temporal Patterns over Component-based Systems at Runtime

Long version of the paper accepted for FACS 2014 - The 11th International Symposium on Formal Aspects of Component SoftwareInternational audienceSelf-adaptation allows systems to modify their structure and/or their behaviour depending on the environment and the system itself. Since reconfigurations must not happen at any but in suitable circumstances, guiding and controlling dynamic reconfigurations at runtime is an important issue. This paper contributes to two essential topics of the self-adaptation---a runtime temporal properties evaluation, and a decentralization of control loopsSelf-adaptation allows systems to modify their structure and/or their behaviour depending on the environment and the system itself. Since reconfigurations must not happen at any but in suitable circumstances, guiding and controlling dynamic reconfigurations at runtime is an important issue. This paper contributes to two essential topics of the self-adaptation - a runtime temporal properties evaluation, and a decentralization of control loops. It extends the work on the adaptation of component-based systems at runtime via policies with temporal patterns by providing a) a specific progressive semantics of temporal patterns and b) a decentralised method which is suitable to deal with temporal patterns of component-based systems at runtime

A Formal Framework for Prototyping Executable Semantics in ATL

ATL is a well-established model transformation language both in industry and in academia, where it is used as a reference language for studying different types of model transformations and their properties. In this paper, we discuss current limitations of ATL’s in-place semantics that hamper its application for modelling and verifying systems and propose a new in-place semantics for ATL that enables it as a specification language for simulating and verifying EMF-based systems. Our approach is based on FMA-ATL, an executable specification of a large excerpt of ATL in Maude, which has been augmented with the new in-place semantics so that Maude’s verification tools can then be used both to perform bounded model checking of invariants and to model check LTL formulas in the resulting system models, where appropriate. Furthermore, FMA-ATL uses ATL as front-end language and it can be reused as-is for verification, including its tool support

Reachability predicates for graph assertions

We introduce a logic-based formalism to specify updates on arbitrary graphs. For the resulting language called GLog, we introduce an assertional language for reasoning about infinite sets of graph configurations in which we use reachability predicates to specify paths of arbitrary length. For the considered assertional language and a restricted class of update rules, we define a symbolic procedure to compute predecessor configurations

Throughput analysis of synchronous data flow graphs

Synchronous Data Flow Graphs (SDFGs) are a useful tool for modeling and analyzing embedded data flow applications, both in a single processor and a multiprocessing context or for application mapping on platforms. Throughput analysis of these SDFGs is an important step for verifying throughput requirements of concurrent real-time applications, for instance within design-space exploration activities. Analysis of SDFGs can be hard, since the worst-case complexity of analysis algorithms is often high. This is also true for throughput analysis. In particular, many algorithms involve a conversion to another kind of data flow graph, the size of which can be exponentially larger than the size of the original graph. In this paper, we present a method for throughput analysis of SDFGs, based on explicit state-space exploration and we show that the method, despite its worst-case complexity, works well in practice, while existing methods often fail. We demonstrate this by comparing the method with state-ofthe- art cycle mean computation algorithms. Moreover, since the state-space exploration method is essentially the same as simulation of the graph, the results of this paper can be easily obtained as a byproduct in existing simulation tools

Graph-Rewriting Petri Nets

Controlled graph rewriting enhances expressiveness of plain graph-rewriting systems (i.e., sets of graph-rewriting rules) by introducing additional constructs for explicitly controlling graph-rewriting rule applications. In this regard, a formal semantic foundation for controlled graph rewriting is inevitable as a reliable basis for tool-based specification and automated analysis of graph-based algorithms. Although several promising attempts have been proposed in the literature, a comprehensive theory of controlled graph rewriting capturing semantic subtleties of advanced control constructs provided by practical tools is still an open challenge. In this paper, we propose graph-rewriting Petri nets (GPN) as a novel foundation for unifying control-flow and rule-application semantics of controlled graph rewriting. GPN instantiate coloured Petri nets with categorical DPO-based graph-rewriting theory where token colours denote typed graphs and graph morphisms and transitions define templates for guarded graph-rewriting rule applications. Hence, GPN enjoy the rich body of specification and analysis techniques of Petri nets including inherent notions of concurrency. To demonstrate expressiveness of GPN, we present a case study by means of a topology-control algorithm for wireless sensor networks